Transition metal complexes with bridged carbene ligands and use thereof in OLEDs

ABSTRACT

Bridged cyclometalated carbene complexes, a process for preparing the bridged cyclometalated carbene complexes, the use of the bridged cyclometalated carbene complexes in organic light-emitting diodes, organic light-emitting diodes comprising at least one inventive bridged cyclometalated carbene complex, a light-emitting layer comprising at least one inventive bridged cyclometalated carbene complex, organic light-emitting diodes comprising at least one inventive light-emitting layer and devices which comprise at least one inventive organic light-emitting diode.

The present invention relates to bridged cyclometalated carbenecomplexes, to a process for preparing the bridged cyclometalated carbenecomplexes, to the use of the bridged cyclometalated carbene complexes inorganic light-emitting diodes, to organic light-emitting diodescomprising at least one inventive bridged cyclometalated carbenecomplex, to a light-emitting layer comprising at least one inventivebridged cyclometalated carbene complex, to organic light-emitting diodescomprising at least one inventive light-emitting layer and to deviceswhich comprise at least one inventive organic light-emitting diode.

Organic light-emitting diodes (OLEDs) exploit the property of materialsof emitting light when they are excited by electrical current. OLEDs areof interest especially as an alternative to cathode ray tubes andliquid-crystal displays for the production of flat visual display units.Owing to the very compact design and the intrinsically low powerconsumption, the devices comprising OLEDs are suitable especially formobile applications, for example for uses in cellphones, laptops, etc.

The basic principles of the way in which OLEDs work and suitableassemblies (layers) of OLEDs are specified, for example, in WO2005/113704 and the literature cited therein.

The prior art has already proposed numerous materials which emit lighton excitation by electrical current.

WO 2005/019373 for the first time discloses the use of unchargedtransition metal complexes which comprise at least one carbene ligand inOLEDs. According to WO 2005/019373, these transition metal complexes canbe used in any layer of an OLED, the ligand structure or central metalbeing variable for adjustment to desired properties of the transitionmetal complexes. For example, the use of the transition metal complexesin a blocking layer for electrons, a blocking layer for excitons, ablocking layer for holes, or the light-emitting layer of the OLED ispossible, preference being given to using the transition metal complexesas emitter molecules in OLEDs.

WO 2006/056418 discloses the use of uncharged transition metal-carbenecomplexes, wherein the carbene ligand used may be a bridged carbeneligand. Suitable bridged carbene ligands have the following generalformula:

where the asterisk denotes the carbon atom or suitable heteroatom of thebridge A in the α position to the n-bonded vinylic carbon atom, and Bdenotes the bridge composed of an alkyl, alkenyl, alkynyl, aryl orheteroaryl radical (Y¹) and a chemical single bond, C(Y⁴)₂, C(O), O, S,S(O), SO₂ or NY⁵.

WO 2005/113704 relates to carbene-metal complexes for use in OLEDs.Among the numerous suitable carbene ligands mentioned, two bridgedligands are mentioned:

Application WO 2007/115981, which has an earlier priority date but hadnot been published at the priority date of the present application,discloses heteroleptic carbene complexes comprising both carbene ligandsand heterocyclic non-carbene ligands. The carbene ligands may be bridgedcarbene ligands, and the bridged carbene ligands mentioned include thoseof the following formulae:

WO 2007/095118 relates to metal complexes of cyclometalatedimidazo[1,2-f]phenanthridine and diimidazo[1,2-a:1′,2′-c]quinazolineligands, and also isoelectronic and benzofused analogs thereof.According to WO 2007/095118, blue-phosphorescing OLEDs with prolongedlifetime are to be provided.

Even though bridged carbene complexes which are suitable for use inOLEDs, especially as light-emitting substances, are already known, theprovision of more stable and/or more efficient compounds which areusable industrially is desirable.

In the context of the present application, electroluminescence isunderstood to mean both electrofluorescence and electrophosphorescence.

It is therefore an object of the present application to provide bridgedcarbene complexes which are suitable for use in OLEDs. In particular,the provision of transition metal complexes which exhibit a propertyspectrum improved over known transition metal complexes, for exampleimproved efficiencies and/or an improved lifetime/stability, isdesirable.

This object is achieved by the provision of bridged cyclometalatedcarbene complexes of the general formula (I)

in which the symbols are each defined as follows:

-   M is a metal atom selected from the group consisting of metals of    group IB, IIB, IIIB, IVB, VB, VIIB, VIIB, VIIIB, the lanthanides and    IIIA of the Periodic Table of the Elements (CAS version) in any    oxidation state possible for the appropriate metal atom; preferably    Fe, Os, Co, Rh, Ir, Ni, Ru, Pd and Pt, Cu, Au, Ce, Tb, Eu, more    preferably Os, Ru, Rh, Ir and Pt and most preferably Ir, Os and Pt;-   K is an uncharged mono- or bidentate ligand;-   L is a mono- or dianionic ligand, preferably a monoanionic ligand,    which may be mono- or bidentate;-   X is CR¹ or N, preferably N;-   Y is NR² or CR² ₂;-   A, D, G, E, A′, D′, G′ and E′    -   are each independently CH, CR³ or N;-   R¹ is F, CN, C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,    C₆-C₃₀-arylthio, substituted or unsubstituted C₆-C₃₀-aryl or    substituted or unsubstituted heteroaryl having from 5 to 30 ring    atoms;-   R², R³    -   are each independently substituted or unsubstituted        C₁-C₂₀-alkyl, substituted or unsubstituted C₅-C₂₀-cycloalkyl,        substituted or unsubstituted C₅-C₂₀-cycloalkenyl, substituted or        unsubstituted heterocycloalkyl having from 5 to 30 ring atoms,        substituted or unsubstituted heterocycloalkenyl having from 5 to        30 ring atoms, substituted or unsubstituted C₂-C₂₀-alkenyl,        substituted or unsubstituted C₂-C₂₀-alkynyl, substituted or        unsubstituted C₆-C₃₀-aryl, substituted or unsubstituted        heteroaryl having from 5 to 30 ring atoms or a substituent with        donor or acceptor action selected from the group consisting of:        C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,        C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals, halogenated        C₁-C₂₀-alkyl radicals, carbonyl (—CO(R⁴)), carbonylthio        (—C═O(SR⁴)), carbonyloxy (—C═O(OR⁴)), oxycarbonyl (—OC═O(R⁴)),        thiocarbonyl (—SC═O(R⁴)), amino (—NR⁴R⁵), OH, pseudohalogen        radicals, amido (—CO═O(NR⁴R⁵)), —NR⁴C═O(R⁵), phosphonate        (—P(O)(OR⁴)₂), phosphate (—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵),        phosphine oxide (—P(O)R⁴ ₂), sulfate (—OS(O)₂OR⁴), sulfoxide        (—S(O)R⁴), sulfonate (—S(O)₂OR⁴), sulfonyl (—S(O)₂R⁴),        sulfonamide (—S(O)₂NR⁴R⁵), NO₂, boronic esters (—B(OR⁴)₂), imino        (—C═NR⁴R⁵), borane radicals, stannate radicals, hydrazine        radicals, hydrazone radicals, oxime radicals, nitroso groups,        diazo groups, vinyl groups, sulfoximines, alanes, germanes,        boroxines and borazines;    -   or    -   two adjacent R³ radicals together form a saturated or        unsaturated, substituted or unsubstituted bridge composed of        from 3 to 6 atoms, such that the R³ radicals together with one        of the elements A=D, D-E, A′=D′, D′-E′, E′=G′ form a 5- to        8-membered ring;-   or    -   the R³ radicals at the G′ and A positions together form a        saturated or unsaturated, substituted or unsubstituted bridge        composed of from 1 to 4 atoms, such that the R³ radicals        together with the element -G′-C—C-A- form a 5- to 8-membered        ring;-   R⁴, R⁵, R⁶    -   are each independently H, substituted or unsubstituted        C₁-C₂₀-alkyl or substituted or unsubstituted C₆-C₃₀-aryl or        substituted or unsubstituted heteroaryl having from 5 to 30 ring        atoms;-   n is the number of carbene ligands, where n is at least 1 and the    carbene ligands in the complex of the formula I, when n>1, may be    the same or different;-   m is the number of ligands K, where m may be 0 or ≧1, and the    ligands K, when m>1, may be the same or different;-   o is the number of ligands L, where o may be 0 or 1, and the ligands    L, when o>1, may be the same or different;    where the sum of n+m+o depends on the oxidation state and    coordination number of the metal atom used and on the denticity of    the ligands L and K, and also on the charge of the ligands L, with    the condition that n is at least 1.

The inventive bridged cyclometalated carbene complexes of the formula Iare notable in that they have a bridge of the carbene ligand(s) and,especially in the X position, a nitrogen atom or a —C—F, —C—CN,—C—C₁-C₂₀-alkoxy, —C—C₆-C₃₀-aryloxy, —C—C₁-C₂₀-alkylthio,—C—C₆-C₃₀-arylthio, substituted or unsubstituted —C—C₆-C₃₀-aryl orsubstituted or unsubstituted —C-heteroaryl radical having from 5 to 30ring atoms. It has been found that the inventive carbene complexes arenotable for good stability and, with the aid of the inventive carbenecomplexes of the formula I, OLEDs are obtainable with an improvedproperty spectrum, for example improved efficiencies and/or an improvedlifetime.

Substituted or unsubstituted C₁-C₂₀-alkyl is understood to mean alkylradicals having from 1 to 20 carbon atoms. Preference is given to C₁- toC₁₀-alkyl radicals, particular preference to C₁- to C₆-alkyl radicals.The alkyl radicals may be either straight-chain or branched. Inaddition, the alkyl radicals may be substituted by one or moresubstituents selected from the group consisting of C₁-C₂₀-alkyl,C₁-C₂₀-alkoxy, halogen, preferably F, C₁-C₂₀-haloalkyl, e.g. CF₃, andC₆-C₃₀-aryl, which may in turn be substituted or unsubstituted. Suitablearyl substituents and suitable alkoxy and halogen substituents arespecified below. Examples of suitable alkyl groups are methyl, ethyl,propyl, butyl, pentyl, hexyl, heptyl and octyl, and also derivatives ofthe alkyl groups mentioned substituted by C₁-C₂₀-alkyl, C₆-C₃₀-aryl,C₁-C₂₀-alkoxy and/or halogen, especially F, for example CF₃. This alsocomprises both the n-isomers of the radicals mentioned and branchedisomers such as isopropyl, isobutyl, isopentyl, sec-butyl, tert-butyl,neopentyl, 3,3-dimethylbutyl, 3-ethylhexyl, etc. Preferred alkyl groupsare methyl, ethyl, isopropyl, tert-butyl and CF₃.

Substituted or unsubstituted C₅-C₂₀-cycloalkyl is understood to meancycloalkyl groups having from 5 to 20, preferably from 5 to 10, morepreferably from 5 to 8 carbon atoms in the base skeleton (ring).Suitable substituents are the substituents mentioned for the alkylgroups. Examples of suitable cycloalkyl groups, which may beunsubstituted or substituted by the radicals specified above for thealkyl groups, are cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl,cyclononyl and cyclodecyl. If appropriate, they may also be polycyclicring systems such as decalinyl, norbornyl, bornanyl or adamantyl.

Substituted or unsubstituted C₅-C₂₀-cycloalkenyl is understood to meancycloalkenyl groups having from 5 to 20, preferably from 5 to 10, morepreferably from 5 to 8 carbon atoms in the base skeleton (ring).Suitable substituents are the substituents mentioned for the alkylgroups. The cycloalkenyl groups may have one double bond or—depending onthe ring size—more than one double bond within the cycloalkenyl ring.The double bonds may be conjugated or nonconjugated. The cycloalkenylgroups preferably have one double bond within the cycloalkenyl ring.Examples of suitable cycloalkenyl groups, which may be unsubstituted orsubstituted by the radicals specified above for the alkyl groups, arecyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclononenyland cyclodecenyl. If appropriate, they may also be polycyclic ringsystems, in which case at least one of the rings is a cycloalkenyl ring.

Substituted or unsubstituted heterocycloalkyl having from 5 to 30 ringatoms is understood to mean heterocycloalkyl groups having from 5 to 30,preferably from 5 to 10, more preferably from 5 to 8 ring atoms, atleast one carbon atom in the heterocycloalkyl base skeleton beingreplaced by a heteroatom. Preferred heteroatoms are N, O and S. Suitablesubstituents are the substituents mentioned for the alkyl groups.Examples of suitable heterocycloalkyl groups, which may be unsubstitutedor substituted by the radicals specified above for the alkyl groups, areradicals derived from the following heterocycles: pyrrolidine, thiolane,tetrahydrofuran, 1,2-oxathiolane, oxazolidine, piperidine, thiane,oxane, dioxane, 1,3-dithiane, morpholine, piperazine. If appropriate,they may also be polycyclic ring systems.

Substituted or unsubstituted heterocycloalkenyl having from 5 to 30 ringatoms is understood to mean heterocycloalkenyl groups having from 5 to30, preferably from 5 to 10, more preferably from 5 to 8 ring atoms, atleast one carbon atom in the heterocycloalkenyl base skeleton beingreplaced by a heteroatom and at least one double bond being present inthe heterocycloalkenyl base skeleton. The heterocycloalkenyl groups mayhave one double bond or—depending on the ring size—more than one doublebond within the heterocycloalkenyl ring. The double bonds may beconjugated or nonconjugated. The heterocycloalkenyl groups preferablyhave one double bond within the heterocycloalkenyl ring. Preferredheteroatoms are N, O and S. Suitable substituents are the substituentsmentioned for the alkyl groups.

Substituted or unsubstituted C₂-C₂₀-alkenyl is understood to meanalkenyl radicals having from 2 to 20 carbon atoms. Preference is givento C₂- to C₁₀-alkenyl radicals, particular preference to C₂- toC₆-alkenyl radicals. The alkenyl radicals may be either straight-chainor branched. In addition, the alkenyl radicals may be substituted by oneor more of the substituents mentioned for the alkyl radicals. Thealkenyl radicals may—depending on the chain length—have one or moredouble bonds, in which case the double bonds may be conjugated to oneanother or be isolated from one another. Examples of suitable alkenylgroups are ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl andoctenyl, where the double bond may be present at any position in theaforementioned radicals, and also derivatives of the alkenyl groupsmentioned substituted by C₁-C₂₀-alkyl, C₁-C₂₀-haloalkyl, C₆-C₃₀-aryl,C₁-C₂₀-alkoxy and/or halogen, especially F.

Substituted or unsubstituted C₂-C₂₀-alkynyl is understood to meanalkynyl radicals having from 2 to 20 carbon atoms. Preference is givento C₂- to C₁₋₁₀-alkynyl radicals, particular preference to C₂- toC₆-alkynyl radicals. The alkynyl radicals may be either straight-chainor branched. In addition, the alkynyl radicals may be substituted by oneor more of the substituents mentioned for the alkyl radicals. Thealkynyl radicals may—depending on the chain length—have one or moretriple bonds, in which case the triple bonds may be conjugated to oneanother or be isolated from one another. Examples of suitable alkynylgroups are ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl andoctyntyl, where the triple bond may be present at any position in theaforementioned radicals, and also derivatives of the alkynyl groupsmentioned substituted by C₁-C₂₀-alkyl, C₁-C₂₉-haloalkyl, C₆-C₃₀-aryl,C₁-C₂₀-alkoxy and/or halogen, especially F.

Suitable C₁-C₂₀-alkoxy and C₁-C₂₀-alkylthio groups derivecorrespondingly from the aforementioned C₁-C₂₀-alkyl radicals. Exampleshere include OCH₃, OC₂H₆, OC₃H₇, OC₄H₉ and OC₈H₁₇, and SCH₃, SC₂H₅,SC₃H₇, SC₄H₉ and SC₈H₁₇. C₃H₇, C₄H₉ and C₈H₁₇ comprise both then-isomers and branched isomers such as isopropyl, isobutyl, sec-butyl,tert-butyl and 2-ethylhexyl. Particularly preferred alkoxy or alkylthiogroups are methoxy, ethoxy, n-octyloxy, 2-ethylhexyloxy and SCH₃.

Suitable halogen radicals or halogen substituents in the context of thepresent application are fluorine, chlorine, bromine and iodine,preferably fluorine, chlorine and bromine, more preferably fluorine andchlorine, most preferably fluorine.

Suitable pseudohalogen radicals in the context of the presentapplication are CN, SCN, OCN, N₃ and SeCN, preference being given to CNand SCN. Very particular preference is given to CN.

C₆-C₃₀-Aryl refers in the present invention to radicals which arederived from monocyclic, bicyclic or tricyclic aromatics and do notcomprise any ring heteroatoms. When the systems are not monocyclicsystems, the saturated form (perhydro form) or the partly unsaturatedform (for example the dihydro form or tetrahydro form), where theparticular forms are known and stable, is also possible for the secondring in the term “aryl”. This means that the term “aryl” in the presentinvention also comprises, for example, bicyclic or tricyclic radicals inwhich either both or all three radicals are aromatic, and also bicyclicor tricyclic radicals in which only one ring is aromatic, and tricyclicradicals in which two rings are aromatic. Examples of aryl are: phenyl,naphthyl, indanyl, 1,2-dihydronaphthenyl, 1,4-dihydronaphthenyl,indenyl, anthracenyl, phenanthrenyl or 1,2,3,4-tetrahydronaphthyl.Particular preference is given to C₆-C₁₀-aryl radicals, for examplephenyl or naphthyl, very particular preference to C₆-aryl radicals, forexample phenyl.

The C₆-C₃₀-aryl radicals may be unsubstituted or substituted by one ormore further radicals. Suitable further radicals are selected from thegroup consisting of C₁-C₂₀-alkyl, C₆-C₃₀-aryl or substituents with donoror acceptor action, suitable substituents with donor or acceptor actionbeing specified below. The C₆-C₃₀-aryl radicals are preferablyunsubstituted or substituted by one or more C₁-C₂₀-alkyl groups,C₁-C₂₀-alkoxy groups, CN, CF₃, F or amino groups (NR⁴R⁵ where suitableR⁴ and R⁵ radicals have been specified above). Further preferredsubstitutions of the C₆-C₃₀-aryl radicals depend on the end use of thecompounds of the general formula (I) and are specified below.

Suitable C₆-C₃₀-aryloxy, C₆-C₃₀-arylthio radicals derive correspondinglyfrom the aforementioned C₆-C₃₀-aryl radicals. Particular preference isgiven to phenoxy and phenylthio.

Unsubstituted or substituted heteroaryl having from 5 to 30 ring atomsis understood to mean monocyclic, bicyclic or tricyclic heteroaromaticswhich can be derived partly from the aforementioned aryl, in which atleast one carbon atom in the aryl base skeleton has been replaced by aheteroatom. Preferred heteroatoms are N, O and S. More preferably, theheteroaryl radicals have 5 to 13 ring atoms. Especially preferably, thebase skeleton of the heteroaryl radicals is selected from systems suchas pyridine and five-membered heteroaromatics such as thiophene,pyrrole, imidazole, thiazole, oxazole or furan. These base skeletons mayoptionally be fused to one or two six-membered aromatic radicals.Suitable fused heteroaromatics are carbazolyl, benzimidazolyl,benzofuryl, benzothiazole, benzoxazole, dibenzofuryl ordibenzothiophenyl.

The base skeleton may be substituted at one, more than one or allsubstitutable positions, suitable substituents being the same as havealready been mentioned under the definition of C₆-C₃₀-aryl. However, theheteroaryl radicals are preferably unsubstituted. Suitable heteroarylradicals are, for example, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl,thiophen-2-yl, thiophen-3-yl, pyrrol-2-yl, pyrrol-3-yl, furan-2-yl,furan-3-yl, thiazol-2-yl, oxazol-2-yl and imidazol-2-yl, and thecorresponding benzofused radicals, especially carbazolyl,benzimidazolyl, benzofuryl, benzothiazole, benzoxazole, dibenzofuryl ordibenzothiophenyl.

In the context of the present application, groups with donor or acceptoraction are understood to mean the following groups:

C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio,SiR⁴R⁵R⁶, halogen radicals, halogenated C₁-C₂₀-alkyl radicals, carbonyl(—CO(R⁴)), carbonylthio (—C═O(SR⁴)), carbonyloxy (—C═O(OR⁴)),oxycarbonyl (—OC═O(R⁴)), thiocarbonyl (—SC═O(R⁴)), amino (—NR⁴R⁵), OH,pseudohalogen radicals, amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵), phosphonate(—P(O)(OR⁴)₂), phosphate (—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵), phosphineoxide (—P(O)R⁴ ₂), sulfate (—OS(O)₂OR⁴), sulfoxide (—S(O)R⁴), sulfonate(—S(O)₂OR⁴), sulfonyl (—S(O)₂R⁴), sulfonamide (—S(O)₂NR⁴R⁵), NO₂,boronic esters (—OB(OR⁴)₂), imino (—C═NR⁴R⁵), borane radicals, stannateradicals, hydrazine radicals, hydrazone radicals, oxime radicals,nitroso groups, diazo groups, vinyl groups, sulfoximines, alanes,germanes, boroxines and borazines.

Preferred substituents with donor or acceptor action are selected fromthe group consisting of:

C₁-C₂₀-alkoxy, preferably C₁-C₆-alkoxy, more preferably ethoxy ormethoxy; C₆-C₃₀-aryloxy, preferably C₆-C₁₀-aryloxy, more preferablyphenyloxy; SiR⁴R⁵R⁶ where R⁴, R⁵ and R⁶ are preferably eachindependently substituted or unsubstituted alkyl or substituted orunsubstituted phenyl, suitable substituents having been specified above;halogen radicals, preferably F, Cl, Br, more preferably F or Cl, mostpreferably F, halogenated C₁-C₂₀-alkyl radicals, preferably halogenatedC₁-C₆-alkyl radicals, most preferably fluorinated C₁-C₆-alkyl radicals,e.g. CF₃, CH₂F, CHF₂ or C₂F₅; amino, preferably dimethylamino,diethylamino or diphenylamino; OH, pseudohalogen radicals, preferablyCN, SCN or OCN, more preferably CN, —C(O)OC₁-C₄-alkyl, preferably—C(O)OMe, P(O)R₂, preferably P(O)Ph₂ and SO₂R₂, preferably SO₂Ph.

Very particularly preferred substituents with donor or acceptor actionare selected from the group consisting of methoxy, phenyloxy,halogenated C₁-C₄-alkyl, preferably CF₃, CH₂F, CHF₂, C₂F₅, halogen,preferably F, CN, SiR⁴R⁵R⁶ where suitable R⁴, R⁵ and R⁶ radicals havealready been specified, diphenylamino, —C(O)OC₁-C₄-alkyl, preferably—C(O)OMe, P(O)Ph₂ and SO₂Ph.

The aforementioned groups with donor or acceptor action are not intendedto rule out the possibility that further radicals and groups among thosespecified above may also have donor or acceptor action. For example, theaforementioned heteroaryl radicals are likewise groups with donor oracceptor action, and the C₁-C₂₀-alkyl radicals are groups with donoraction.

The R⁴, R⁵ and R⁶ radicals mentioned in the aforementioned groups withdonor or acceptor action are each as already defined above, i.e. R⁴, R⁵and R⁶ are each independently:

Hydrogen, substituted or unsubstituted C₁-C₂₀-alkyl or substituted orunsubstituted C₆-C₃₀-aryl or substituted or unsubstituted heteroarylhaving from 5 to 30 ring atoms, suitable and preferred alkyl and arylradicals having been specified above. More preferably, the R⁴, R⁵ and R⁶radicals are each C₁-C₆-alkyl, e.g. methyl, ethyl, i-propyl, tert-butyl,or phenyl or pyridyl.

The metal atom M in the inventive bridged cyclometalated carbenecomplexes of the general formula I is selected from the group consistingof metals of group IB, IIB, IIIB, IVB, VB, VIIB, VIIB, VIIIB, thelanthanides and IIIA of the Periodic Table of the Elements (CAS version)in any oxidation state possible for the appropriate metal atom;preferably Fe, Os, Co, Rh, Ir, Ni, Ru, Pd and Pt, Cu, Au, Ce, Tb, Eu,more preferably Os, Ru, Rh, Ir and Pt and most preferably Ir, Os and Pt,in any oxidation state possible for the appropriate metal atom.

More preferably, the metal M is selected from the group consisting ofIr, Os and Pt, preference being given to Os(II), Ir(III) and Pt(II).Particular preference is given to Ir(II).

The number of carbene ligands n and the numbers m and o of any ligands Kand L present depend on the oxidation state and the coordination numberof the metal M, and on the denticity and the charge of the ligands L,where at least one carbene ligand is present in the inventive carbenecomplexes of the formula I, i.e. n is at least 1.

Preferred embodiments of inventive carbene complexes of the formula Idepending on the charge and coordination number of the metal M used aredescribed hereinafter:

In the case that M is a metal with a coordination number of 4 (e.g.Pt(II) or Pd(II), Rh(I)), the inventive carbene complexes of the formulaI have one or two carbene ligands, i.e. n is 1 or 2, where, in the casethat n is 1 and M is a metal with a coordination number of 4, onemonoanionic bidentate ligand L is present as well as the carbene ligandin the inventive carbene complexes, i.e. o is 1. In the case that M is ametal with a coordination number of 6 (e.g. Ir(III), Co(II), Co(III),Rh(III), Os(II), Pt(IV)), the inventive carbene complexes of the formulaI, depending on their charge, preferably have one, two or three,preferably two or three, carbene ligands of the general formula I whichmay be the same or different, i.e. n is 1, 2 or 3, preferably 2 or 3.For example, n in the case of Ir(III), Co(III) or Rh(III) is generally1, 2 or 3, where, in the case that n=1, two additional monoanionicbidentate ligands L are present, i.e. o is 2. In the case that n=2, theaforementioned carbene complexes have one additional monoanionicbidentate ligand L, i.e. o is 1. In the case that n=3, which isparticularly preferred, the aforementioned carbene complexes do not haveany further ligands K and L, i.e. m and o are each 0. In the case ofOs(II), n is generally 1 or 2, where, in the case that n=1, oneadditional monoanionic bidentate ligand L and one additional unchargedbidentate ligand K are present, i.e. o is 1 and m is 1. In the case thatn=2, which is particularly preferred, the aforementioned carbenecomplexes have one additional uncharged bidentate ligand K, i.e. m is 1.When the metal atom M has a coordination number of 8 or more, theinventive carbene complexes of the general formula I, as well as one,two or three carbene ligands, may have either one or more furthercarbene ligands and/or one or more additional ligands K and/or L. In apreferred embodiment, the present invention relates to bridgedcyclometalated carbene complexes of the general formula I which have ametal M with a coordination number of 6, preferably Ir(III), where n=3and m and o are each 0.

Depending on the coordination number of the metal M used and the numbern of carbene ligands used and the numbers m and o of the additionalligands K and L which may be used, different isomers of thecorresponding metal complexes with the same metal M and the same natureof the carbene ligands used and additional may be present. For example,in the case of complexes with a metal M with coordination number 6 (i.e.octahedral complexes), for example Ir(III) complexes, “fac-mer isomers”(facial/meridional isomers) are possible when the complexes are those ofthe general composition M(AB)₃ where AB are bidentate ligands. In thecontext of the present application, “fac-mer isomers” are understood tomean the isomers shown below:

In the case of square-planar complexes with a metal M with thecoordination number of 4, for example Pt(II) complexes, “cis/transisomers” are possible when the complexes are those of the generalcomposition M(AB)₂, where AB are bidentate ligands. In the context ofthe present application “isomers” are understood to mean the isomersshown below:

The symbols A and B are each one binding site of a ligand, onlybidentate ligands being present. According to the aforementioned generalcomposition, a bidentate ligand has two A groups and two B groups.

It is known in principle to those skilled in the art what is meant bycis/trans and fac-mer isomers. In complexes of the composition MA₃B₃,three groups of the same type may either occupy the corners of oneoctahedral face (facial isomer) or a meridian, i.e. two of the threeligand binding sites are trans to one another (meridional isomer). Withregard to the definition of cis/trans isomers and fac-mer isomers inoctahedral metal complexes, see, for example, J. Huheey, E. Keiter, R.Keiter, Anorganische Chemie: Prinzipien von Struktur und Reaktivitat[Inorganic Chemistry: Principles of Structure and Reactivity], 2nd,newly revised edition, translated into German and extended by RalfSteudel, Berlin; New York: de Gruyter, 1995, pages 575, 576.

In the case of square-planar complexes, cis-isomerism means that, incomplexes of the composition MA₂B₂, both the two A groups and the two Bgroups occupy adjacent corners of a square, while both the two A groupsand the two B groups in the case of trans isomerism each occupy the twomutually diagonally opposite corners of a square. With regard to thedefinition of cis/trans isomers in square-planar metal complexes, see,for example, J. Huheey, E. Keiter, R. Keiter, Anorganische Chemie:Prinzipien von Struktur und Reaktivität, 2nd, newly revised edition,translated into German and expanded by Ralf Steudel, Berlin; New York:de Gruyter, 1995, pages 557 to 559.

In general, the different isomers of the inventive carbene complexes ofthe formula I can be separated by processes known to those skilled inthe art, for example by chromatography, sublimation or crystallization.

The present invention thus relates both to the individual isomers of thecarbene complexes of the formula I in each case and to mixtures ofdifferent isomers in any mixing ratio.

The number n of carbene ligands in the inventive bridged cyclometalatedcarbene complexes of the formula I in which the transition metal atom Mhas a coordination number of 6 and the oxidation state of III,particular preference being given to Ir(III), is preferably 3, and thenumbers m and o of the additional ligands K and L in these complexes arepreferably each 0.

The number n of carbene ligands in the inventive bridged cyclometalatedcarbene complexes of the formula I in which the transition metal atom Mhas a coordination number of 6 and the oxidation state of II, particularpreference being given to Os(II), is preferably 2, in which case oneadditional uncharged bidentate ligand K is present, i.e. m ispreferably 1. o in these complexes is preferably 0.

The number n of carbene ligands in the inventive bridged cyclometalatedcarbene complexes of the formula I in which the transition metal atom Mhas a coordination number of 4, particular preference being given toPt(II), is preferably 1 or 2, where, in the case that n=1, preferablyone additional monoanionic bidentate ligand L is present, i.e. o islikewise preferably 1 and m is preferably O. In the case that n=2, m ando are preferably each 0.

In a very particularly preferred embodiment, M in the carbene complexesof the formula I is Ir(III), n is 3 and m and o are each 0.

The n carbene ligands in the carbene complex when n>1 may be the same ordifferent. They are preferably the same, i.e., in the case thatM=Ir(III) and n=3, the three carbene ligands are preferably the same.

Suitable mono- or dianionic ligands L, preferably monoanionic ligands L,which may be mono- or bidentate, are the ligands typically used as mono-or bidentate, mono- or dianionic ligands.

Suitable monoanionic monodentate ligands are, for example, halides,especially Cl⁻ and Br⁻, pseudohalides, especially CN⁻, cyclopentadienyl(Cp⁻), hydride, alkoxy, aryloxy, alkyl radicals which are bonded to thetransition metal M via a sigma bond, for example CH₃, alkylaryl radicalswhich are bonded to the transition metal M¹ via a sigma bond, forexample benzyl.

Suitable monoanionic bidentate ligands are, for example, acetylacetonateand derivatives thereof, picolinate, Schiff bases, amino acids,arylazoles, e.g. phenylpyridine, and the further bidentate monoanionicligands specified in WO 02/15645, preference being given toacetylacetonate and picolinate.

Suitable dianionic bidentate ligands are, for example, dialkoxides,dicarbonates, dicarboxylates, diamides, diimides, dithiolates,biscyclopentadienyls, bisphosphonates, bissulfonates and3-phenylpyrazole.

Suitable uncharged mono- or bidentate ligands K are preferably selectedfrom the group consisting of phosphines, both mono- and bisphosphines;phosphonates, both mono- and bisphosphonates, and derivatives thereof,arsenates, both mono- and bisarsenates, and derivatives thereof;phosphites, both mono- and bisphosphites; CO; pyridines, both mono- andbispyridines; nitriles, dinitriles, allyl, diimines, unconjugated dienesand conjugated dienes which form a π-complex with M¹. Particularlypreferred uncharged mono- or bidentate ligands K are selected from thegroup consisting of phosphines, both mono- and bisphosphines, preferablytrialkyl-, triaryl- or alkylarylphosphines, more preferably PAr₃, whereAr is a substituted or unsubstituted aryl radical and the three arylradicals in PAr₃ may be the same or different, more preferably PPh₃,PEt₃, PnBu₃, PEt₂Ph, PMe₂Ph, PnBu₂Ph; phosphonates and derivativesthereof, arsenates and derivatives thereof, phosphites, CO; pyridines,both mono- and bispyridines, where the pyridines may be substituted byalkyl or aryl groups; nitriles and dienes which form a π-complex withM¹, preferably η⁴-diphenyl-1,3-butadiene, η⁴-1,3-pentadiene,η⁴-1-phenyl-1,3-pentadiene, η⁴-1,4-dibenzyl-1,3-butadiene,η⁴-2,4-hexadiene, η⁴-3-methyl-1,3-pentadiene,η⁴-1,4-ditolyl-1,3-butadiene, η⁴-1,4-bis(trimethylsilyl)-1,3-butadieneand η²- or η⁴-cyclooctadiene (in each case 1,3 and in each case 1,5),more preferably 1,4-diphenyl-1,3-butadiene, 1-phenyl-1,3-pentadiene,2,4-hexadiene, butadiene, η²-cyclooctene, η⁴-1,3-cyclooctadiene andη⁴-1,5-cyclooctadiene. Very particularly preferred uncharged monodentateligands are selected from the group consisting of PPh₃, P(OPh)₃, AsPh₃,CO, pyridine, nitriles and derivatives thereof. Suitable uncharged mono-or bidentate ligands are preferably 1,4-diphenyl-1,3-butadiene,1-phenyl-1,3-pentadiene, 2,4-hexadiene, η⁴-cyclooctadiene andη²-cyclooctadiene (in each case 1,3 and in each case 1,5).

The R¹ radical of the X group in the cyclometalated carbene complexes ofthe formula I is F, CN, C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,C₆-C₃₀-arylthio, substituted or unsubstituted C₆-C₃₀-aryl or substitutedor unsubstituted heteroaryl having from 5 to 30 ring atoms. The R¹radical of the X group is preferably F, CN, C₁- to C₄-alkoxy, morepreferably methoxy, C₆- to C₁₀-aryloxy, more preferably phenoxy, C₁- toC₄-alkylthio, more preferably SCH₃, C₆- to C₁₋₁₀-arylthio, substitutedor unsubstituted phenyl, more preferably unsubstituted phenyl, tolyl,dimethylphenyl, trimethylphenyl, F-, CN-, methoxy- and/orCF₃-substituted phenyl, or substituted or unsubstituted heteroarylhaving from 5 to 13 ring atoms, more preferably pyridyl, thienyl,pyrrolyl, furyl, thiazolyl, oxazolyl, pyrazolyl or imidazolyl. Mostpreferably, the R¹ radical is F, CN or methoxy, phenyl, pyridyl.

The X group in the cyclometalated carbene complexes of the formula I ispreferably N, i.e. the R¹ radical is absent.

The R² and R³ radicals in the bridged cyclometalated carbene complexesof the formula I are each independently substituted or unsubstitutedC₁-C₂₀-alkyl, substituted or unsubstituted C₅-C₂₀-cycloalkyl,substituted or unsubstituted C₅-C₂₀-cycloalkenyl, substituted orunsubstituted heterocycloalkyl having from 5 to 30 ring atoms,substituted or unsubstituted heterocycloalkenyl having from 5 to 30 ringatoms, substituted or unsubstituted C₂-C₂₀-alkenyl, substituted orunsubstituted C₂-C₂₀-alkynyl, substituted or unsubstituted C₅-C₃₀-aryl,substituted or unsubstituted heteroaryl having from 5 to 30 ring atomsor a substituent with donor or acceptor action selected from the groupconsisting of: C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,C₅-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals, halogenated C₁-C₂₀-alkylradicals, carbonyl (—CO(R⁴)), carbonylthio (—C═O(SR⁴)), carbonyloxy(—C═O(OR⁴)), oxycarbonyl (—OC═O(R⁴)), thiocarbonyl (—SC═O(R⁴)), amino(—NR⁴R⁵), OH, pseudohalogen radicals, amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵),phosphonate (—P(O)(OR⁴)₂, phosphate (—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵),phosphine oxide (—P(O)R⁴ ₂), sulfate (—OS(O)₂OR⁴), sulfoxide (—S(O)R⁴),sulfonate (—S(O)₂OR⁴), sulfonyl (—S(O)₂R⁴), sulfonamide (—S(O)₂NR⁴R⁵),NO₂, boronic esters (—B(OR⁴)₂), imino (—C═NR⁴R⁵), borane radicals,stannate radicals, hydrazine radicals, hydrazone radicals, oximeradicals, nitroso groups, diazo groups, vinyl groups, sulfoximines,alanes, germanes, boroxines and borazines;

or

two adjacent R³ radicals together form a saturated or unsaturated,substituted or unsubstituted bridge composed of from 3 to 6 atoms, suchthat the R³ radicals together with one of the elements A=D, D-E, A′=D′,D′-E′, E′=G′ form a 5- to 8-membered ring;

or

the R³ radicals at the G′ and A positions together form a saturated orunsaturated, substituted or unsubstituted bridge composed of from 1 to 4atoms, such that the R³ radicals together with the element -G′-C—C-A-form a 5- to 8-membered ring;

the bridges are preferably unsubstituted (i.e. all substitutablepositions are substituted by hydrogen) or substituted by one or moreradicals selected from the group consisting of C₁-C₄-alkyl, morepreferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl or tert-butyl, substituted or unsubstituted phenyl, preferablyunsubstituted phenyl, tolyl, dimethylphenyl, trimethylphenyl, F-, CN-,methoxy- and/or CF₃-substituted phenyl, substituted or unsubstitutedheteroaryl having from 5 to 13 ring atoms, preferably pyridyl, thienyl,pyrrolyl, furyl or imidazolyl, C₁-C₄-alkoxy, more preferably methoxy,C₆-C₁₀-aryloxy, particularly phenoxy, C₁-C₄-alkylthio, preferably SCH₃,C₆-C₁₀-arylthio, preferably SPh, SiR⁴R⁵R⁶, preferably SiMe₃ or SiPh₃, F,Cl, Br, preferably F, halogenated C₁-C₁₀-alkyl radicals, preferably CF₃,and pseudohalogen radicals, preferably CN; where the bridges arepreferably formed from carbon atoms and optionally have 1 or 2heteroatoms, preferably 1 or 2 nitrogen atoms.

In a preferred embodiment, R² and R³ are each independently selectedfrom the group consisting of substituted or unsubstituted C₁-C₂₀-alkyl,substituted or unsubstituted C₂-C₂₀-alkenyl, substituted orunsubstituted C₂-C₂₀-alkynyl, substituted or unsubstituted C₅-C₃₀-aryl,substituted or unsubstituted heteroaryl having from 5 to 30 ring atoms,C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio,SiR⁴R⁵R⁶, halogen radicals, halogenated C₁-C₂₀-alkyl radicals andpseudohalogen radicals. More preferably, R² and R³ are eachindependently selected from the group consisting of substituted orunsubstituted C₁-C₂₀-alkyl, preferably C₁-C₄-alkyl, more preferablymethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl ortert-butyl, substituted or unsubstituted C₆-C₃₀-aryl, preferablysubstituted or unsubstituted phenyl, more preferably unsubstitutedphenyl, tolyl, dimethylphenyl, trimethylphenyl, F-, CN-, methoxy- and/orCF₃-substituted phenyl, substituted or unsubstituted heteroaryl havingfrom 5 to 30 ring atoms, preferably substituted or unsubstitutedheteroaryl having from 5 to 13 ring atoms, more preferably pyridyl,thienyl, pyrrolyl, furyl, thiazolyl, oxazolyl, pyrazolyl or imidazolyl,C₁-C₂₀-alkoxy, preferably C₁-C₄-alkoxy, more preferably methoxy,C₆-C₃₀-aryloxy, preferably C₆-C₁₀-aryloxy, more preferably phenoxy,C₁-C₂₀-alkylthio, preferably C₁-C₄-alkylthio, more preferably SCH₃,C₆-C₃₀-arylthio, preferably C₆-C₁₀-arylthio, more preferably SPh,SiR⁴R⁵R⁶, preferably SiMe₃ or SiPh₃, halogen radicals, preferably F, Cl,Br, more preferably F, halogenated C₁-C₂₀-alkyl radicals, preferablyhalogenated C₁-C₁₀-alkyl radicals, more preferably CF₃, andpseudohalogen radicals, preferably CN;

or

two adjacent R³ radicals together form a saturated or unsaturated,methyl-, phenyl-, methoxy-, SiMe₃-, SiPh₃-, F-, CF₃- or CN-substitutedor unsubstituted bridge composed of 3 or 4 carbon atoms, such that theR³ radicals together with one of the elements A=D, D-E, A′=D′, D′-E′,E′=G′ form a 5- or 6-membered ring;orthe R³ radicals at the G′ and A positions together form a saturated orunsaturated, methyl-, phenyl-, methoxy-, SiMe₃-, SiPh₃-, F-, CF₃- orCN-substituted or unsubstituted bridge composed of 1 or 2 carbon atoms,such that the R³ radicals together with the element -G′-C—C-A- form a 5-or 6-membered ring.

In a particularly preferred embodiment, R¹ (if the R¹ radical ispresent) and R³ are each as defined above for R¹ and R³ and R² isselected from the group consisting of substituted or unsubstitutedC₁-C₂₀-alkyl which is branched in the 1-position, preferably isopropyl,isobutyl, isopentyl, sec-butyl or tert-butyl; substituted orunsubstituted C₆-aryl, preferably unsubstituted phenyl or phenyl whichis substituted in the 2- and/or 6-position, preferably by methyl,methoxy, CF₃, CN and/or F; more preferably 2-tolyl, 2-methoxyphenyl,2-cyanophenyl, 2-trifluoromethylphenyl, 2,6-difluorophenyl, 2,3-, 2,4-,2,5- or 2,6-dimethylphenyl or 2,4,6-, 2,3,4- or 2,3,5-trimethylphenyl;substituted or unsubstituted heteroaryl having from 5 to 13 ring atoms,preferably pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, thiophen-2-yl,thiophen-3-yl, pyrrol-2-yl, pyrrol-3-yl, furan-2-yl, furan-3-yl,thiazol-2-yl, oxazol-2-yl, pyrazol-3-yl or imidazol-2-yl, and thecorresponding benzofused radicals.

It has been found that carbene complexes of the formula I which have theaforementioned particularly preferred R² radicals have particularly goodstability.

In a preferred embodiment, the present invention relates to bridgedcyclometalated carbene complexes of the formula I in which X is N.Y. ispreferably NR² where suitable R² radicals are as defined above.Particular preference is thus given to carbene complexes of the formulaI in which:

X is N, and

Y is NR²

where R² is as defined above.

The A, D, G, E, A′, D′, G′ and E′ groups in the carbene complexes of theformula I are each independently CH, CR³ or N. Preferably 0, 1 or 2groups, more preferably 0 or 1 group, selected from the A, D, G and Egroups or selected from the A′, D′, G′ and E′ groups, is/are N. In aparticularly preferred embodiment, the A, D, G, E, A′, D′, G′ and E′groups are each CH or CR³, most preferably CH. Suitable R³ radicals arespecified above.

Particularly preferred carbene complexes of the formula I are selectedfrom carbene complexes of the formulae Ia and Ib:

in which:

-   A, D, G, E, A′, D′, G′ and E′    -   are each independently CH, CR³ or N, preferably CH or CR³, more        preferably CH;-   R², R³ are each independently substituted or unsubstituted    C₁-C₂₀-alkyl, substituted or unsubstituted C₅-C₂₀-cycloalkyl,    substituted or unsubstituted C₅-C₂₀-cycloalkenyl, substituted or    unsubstituted heterocycloalkyl having from 5 to 30 ring atoms,    substituted or unsubstituted heterocycloalkenyl having from 5 to 30    ring atoms, substituted or unsubstituted C₂-C₂₀-alkenyl, substituted    or unsubstituted C₂-C₂₀-alkynyl, substituted or unsubstituted    C₆-C₃₀-aryl, substituted or unsubstituted heteroaryl having from 5    to 30 ring atoms or a substituent with donor or acceptor action    selected from the group consisting of: C₁-C₂₀-alkoxy,    C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen    radicals, halogenated C₁-C₂₀-alkyl radicals, carbonyl (—CO(R⁴)),    carbonylthio (—C═O(SR⁴)), carbonyloxy (—C═O(OR⁴)), oxycarbonyl    (—OC═O(R⁴)), thiocarbonyl (—SC═O(R⁴)), amino (—NR⁴R⁵), OH,    pseudohalogen radicals, amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵),    phosphonate (—P(O)(OR⁴))₂, phosphate (—OP(O)(OR⁴)₂), phosphine    (—PR⁴R⁵), phosphine oxide (—P(O)R⁴ ₂), sulfate (−OS(O)₂OR⁴),    sulfoxide (—S(O)R⁴), sulfonate (—S(O)₂OR⁴), sulfonyl (—S(O)₂R⁴),    sulfonamide (—S(O)₂NR⁴R⁵), NO₂, boronic esters (—B(OR⁴)₂), imino    (—C═NR⁴R⁵), borane radicals, stannate radicals, hydrazine radicals,    hydrazone radicals, oxime radicals, nitroso groups, diazo groups,    vinyl groups, sulfoximines, alanes, germanes, boroxines and    borazines;    -   or    -   two adjacent R³ radicals together form a saturated or        unsaturated, substituted or unsubstituted bridge composed of        from 3 to 6 atoms, such that the R³ radicals together with one        of the elements A=D, D-E, A′=D′, D′-E′, E′=G′ form a 5- to        8-membered ring;    -   or    -   the R³ radicals at the G′ and A positions together form a        saturated or unsaturated, substituted or unsubstituted bridge        composed of from 1 to 4 atoms, such that the R³ radicals        together with the element -G′-C—C-A- form a 5- to 8-membered        ring;    -   where R² is preferably selected from the group consisting of        substituted or unsubstituted C₁-C₂₀-alkyl which is branched in        the 1-position, preferably isopropyl, isobutyl, isopentyl,        sec-butyl or tert-butyl; substituted or unsubstituted C₆-aryl,        preferably unsubstituted phenyl or phenyl which is substituted        in the 2- and/or 6-position, preferably by methyl, methoxy, CF₃,        CN and/or F; more preferably 2-tolyl, 2-methoxyphenyl,        2-cyanophenyl, 2-trifluoromethylphenyl, 2,6-difluorophenyl,        2,3-, 2,4-, 2,5- or 2,6-dimethylphenyl or 2,4,6-, 2,3,4- or        2,3,5-trimethylphenyl; substituted or unsubstituted heteroaryl        having from 5 to 13 ring atoms, preferably pyridin-2-yl,        pyridin-3-yl, pyridin-4-yl, thiophen-2-yl, thiophen-3-yl,        pyrrol-2-yl, pyrrol-3-yl, furan-2-yl, furan-3-yl, thiazol-2-yl,        oxazol-2-yl, pyrazol-3-yl or imidazol-2-yl, and the        corresponding benzofused radicals;-   R⁴, R⁵, R⁶    -   are each independently H, substituted or unsubstituted        C₁-C₂₀-alkyl or substituted or unsubstituted C₆-C₃₀-aryl, or        substituted or unsubstituted heteroaryl having from 5 to 30 ring        atoms;-   Y is CR² ₂;-   M is Ir, Os or Pt; preferably Ir(III), Os(II) or Pt(II), more    preferably Ir(III);-   K is an uncharged bidentate ligand;-   L is a monoanionic bidentate ligand;-   n is the number of carbene ligands, where n is 3 in the case of Ir,    is 2 in the case of Os and is 1 or 2 in the case of Pt, and the    carbene ligands in the complexes of the formulae Ia, Ib, Ic and Id    may be the same or different;-   m is 0 in the case that M=Ir or Pt and is 1 in the case of Os;-   o is 0 in the case that M=Ir or Os and Pt and in the case that n=2,    and is 1 in the case of Pt and in the case that n=1.

Particularly preferred radicals, groups and indices M, R², R³, R⁴, R⁵,R⁶, A, D, G, E, A′, D′, G′, E′, Y, M, K, L, n, m and o are specifiedabove. Most preferably, M in the carbene complexes of the formulae Ia,Ib, Ic and Id is Ir(III), n is 3 and m and o are each 0.

Very particular preference is given to carbene complexes of the formulaespecified below:

The aforementioned compounds may optionally be substituted by one ormore further substituents according to the definition of the generalformula I.

The inventive bridged cyclometalated carbene complexes of the formula Ican in principle be prepared analogously to processes known to thoseskilled in the art. Suitable processes for preparing carbene complexesare detailed, for example, in the review articles W. A. Hermann et al.,Advances in Organometallic Chemistry, 2001 vol. 48, 1 to 69, W. A.Hermann et al., Angew. Chem. 1997, 109, 2256 to 2282 and G. Bertrand etal. Chem. Rev. 2000, 100, 39 to 91 and the literature cited therein, andalso in WO 2005/113704, WO 2005/019373 and WO 2007/088093.

In one embodiment, the inventive bridged cyclometalated carbenecomplexes of the formula I are prepared from ligand precursorscorresponding to the carbene ligands and suitable metax complexescomprising the desired metal.

Suitable ligand precursors of the carbene ligands are known to thoseskilled in the art. They are preferably cationic precursors of thecarbene ligands of the general formula III

in which

-   Q⁻ is a monoanionic counterion, preferably halide, pseudohalide, BF₄    ⁻, BPh₄ ⁻, PF₆ ⁻, AsF₆ ⁻ or SbF₆ ⁻;    and    the further radicals, symbols and indices are each as defined above    in the ligand precursor of the general formula III.

The ligand precursors of the general formula III can be preparedanalogously to processes known to those skilled in the art. Suitableprocesses are specified, for example, in WO 2005/019373 and theliterature cited therein, for example Organic Letters, 1999, 1, 953-956;Angewandte Chemie, 2000, 112, 1672-1674. Further suitable processes arespecified, for example, in T. Weskamp et al., J. Organometal. Chem.2000, 600, 12-22; G. Xu et al., Org. Lett. 2005, 7, 4605-4608; V.Lavallo et al., Angew. Chem. Int. Ed. 2005, 44, 5705-5709.

In a preferred embodiment, the present invention relates to a processfor preparing the inventive cyclometalated bridged carbene complexes ofthe general formula I, wherein the preparation comprises the followingstep:

Reaction of at least one ligand precursor of the general formula (III)

in which

-   Q⁻ is a monoanionic counterion, preferably halide, pseudohalide, BF₄    ⁻, BPh₄ ⁻, PF₆ ⁻, AsF₆ ⁻ or SbF₆ ⁻;    and    the further symbols in the ligand precursor of the general formula    III are each defined as follows:-   X is CR¹ or N, preferably N;-   Y is NR² or CR² ₂;-   A, D, G, E, A′, D′, G′ or E′    -   are each independently CH, CR³ or N;-   R¹ is F, CN, C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,    C₆-C₃₀-arylthio, substituted or unsubstituted C₆-C₃₀-aryl or    substituted or unsubstituted heteroaryl having from 5 to 30 ring    atoms;-   R², R³    -   are each independently substituted or unsubstituted        C₁-C₂₀-alkyl, substituted or unsubstituted C₅-C₂₀-cycloalkyl,        substituted or unsubstituted C₅-C₂₀-cycloalkenyl, substituted or        unsubstituted heterocycloalkyl having from 5 to 30 ring atoms,        substituted or unsubstituted heterocycloalkenyl having from 5 to        30 ring atoms, substituted or unsubstituted C₂-C₂₀-alkenyl,        substituted or unsubstituted C₂-C₂₀-alkynyl, substituted or        unsubstituted C₆-C₃₀-aryl, substituted or unsubstituted        heteroaryl having from 5 to 30 ring atoms or a substituent with        donor or acceptor action selected from the group consisting of:        C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,        C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals, halogenated        C₁-C₂₀-alkyl radicals, carbonyl (—CO(R⁴)), carbonylthio        (—C═O(SR⁴)), carbonyloxy (—C═O(OR⁴)), oxycarbonyl (—OC═O(R⁴)),        thiocarbonyl (—SC═O(R⁴)), amino (—NR⁴R⁵), OH, pseudohalogen        radicals, amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵), phosphonate        (—P(O)(OR⁴)₂), phosphate (—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵),        phosphine oxide (—P(O)R⁴ ₂), sulfate (—OS(O)₂OR⁴), sulfoxide        (—S(O)R⁴), sulfonate (—S(O)₂OR⁴), sulfonyl (—S(O)₂R⁴),        sulfonamide (—S(O)₂NR⁴R⁵), NO₂, boronic esters (—B(OR⁴)₂), imino        (—C═NR⁴R⁵), borane radicals, stannate radicals, hydrazine        radicals, hydrazone radicals, oxime radicals, nitroso groups,        diazo groups, vinyl groups, sulfoximines, alanes, germanes,        boroxines and borazines;    -   or    -   two adjacent R³ radicals together form a saturated or        unsaturated, substituted or unsubstituted bridge composed of        from 3 to 6 atoms, such that the R³ radicals together with one        of the elements A=D, D-E, A′=D′, D′-E′, E′=G′ form a 5- to        8-membered ring;    -   or    -   the R³ radicals at the G′ and A positions together form a        saturated or unsaturated, substituted or unsubstituted bridge        composed of from 1 to 4 atoms, such that the R³ radicals        together with the element -G′-C—C-A- form a 5- to 8-membered        ring; and-   R⁴, R⁵, R⁶    -   are each independently H, substituted or unsubstituted        C₁-C₂₀-alkyl or substituted or unsubstituted C₆-C₃₀-aryl or        substituted or unsubstituted heteroaryl having from 5 to 30 ring        atoms;        with a metal complex comprising at least one metal M where M is        defined as follows:-   M is a metal atom selected from the group consisting of metals of    group IB, IIB, IIIB, IVB, VB, VIIB, VIIB, VIIIB, the lanthanides and    IIIA of the Periodic Table of the Elements (CAS version) in any    oxidation state possible for the appropriate metal atom; preferably    Fe, Os, Co, Rh, Ir, Ni, Ru, Pd and Pt, Cu, Au, Ce, Tb, Eu, more    preferably Os, Ru, Rh, Ir and Pt and most preferably Ir, Os and Pt.

Particularly preferred radicals, groups and indices M, R², R³, R⁴, R⁵,R⁶, A, D, G, E, A′, D′, G′, E′, Y, M, K, L, n, m and o have beenspecified above.

If appropriate, the inventive reaction of the ligand precursors of theformula III with the metal complex is effected in the presence ofsuitable ligand precursors of the ligands K and/or L (“one-pot process”)if m and/or o is not 0 in the carbene complexes of the formula I.Suitable ligand precursors of ligands K and L are known to those skilledin the art. Or, if m and/or o is not 0, a sequential reaction iseffected. The sequential reaction can be effected either by reacting themetal complex with at least one carbene ligand precursor of the generalformula III in a first step, in which case a carbene complex which hasat least one carbene ligand in cyclometalated or non-cyclometalated formand has at least one further coordination means (in which case thefurther coordination means is present either through a free coordinationsite on the metal M or through the displacement of other ligands) for atleast one further bidentate ligand K and/or L is initially prepared asan intermediate; or by reacting the metal complex with at least oneligand precursor for the ligands K and/or L in a first step, in whichcase a complex which has at least one ligand K and/or L and at least onefurther coordination means (in which case the further coordination meansis present either through a free coordination site on the metal M′ orthrough the displacement of other ligands) for at least one bidentatecarbene ligand is initially prepared as an intermediate. In a secondstep, which follows the first step, the particular complex obtained inthe first step is reacted with at least one ligand precursor of theligands K and/or L (when at least one carbene ligand precursor has beenused in the first step), or with at least one carbene ligand precursorof the general formula III (when at least one ligand precursor of theligands K and/or L was used in the first step).

In the particularly preferred case that the metal M in the inventivecarbene complexes of the formula I is Ir(III) with a coordination numberof 6 and n=3 and m and o are each 0, a reaction is effected with onecarbene ligand precursor or different carbene ligand precursors of theformula III. When different carbene ligand precursors of the formula IIIare used, the reaction can be effected in the form of a “one-potreaction” or sequentially—as described above using a carbene ligandprecursor and ligand precursors for the ligands K and L. The carbeneligands in the carbene complex of the formula I are preferablyidentical, such that a reaction of the carbene ligand precursor of theformula III is effected with a suitable metal complex.

For the very particularly preferred case (M=Ir(III), n=3), themetal:ligand precursor stoichiometry is generally from 1:3 to 1:9,preferably from 1:3 to 1:6.

In the case that a carbene ligand is present in the inventive carbenecomplexes of the formula I and the metal atom is Ir(III) (M=Ir(III),n=1), the metal:ligand precursor stoichiometry is generally from 1:1 to1:3, preferably from 1:1 to 1:2.

The metal complex comprising at least one metal M is a metal complexcomprising at least one metal selected from the group consisting ofmetals of group IB, IIB, IIIB, IVB, VB, VIIB, VIIB, VIIIB, thelanthanides and IIIA of the Periodic Table of the Elements (CAS version)in any oxidation state possible for the appropriate metal atom;preferably Fe, Os, Co, Rh, Ir, Ni, Ru, Pd and Pt, Cu, Au, Ce, Tb, Eu,more preferably Os, Ru, Rh, Ir and Pt and most preferably Ir, Os and Pt.Preference is given to using Pt(II), Os(II), Ir(I) or Ir(III) in themetal complexes used in the process according to the invention,particular preference being given to Ir(I) and Ir(III) and veryparticular preference to NI). Suitable metal complexes are known tothose skilled in the art. Examples of suitable metal complexes arePt(cod)Cl₂, Pt(cod)Me₂, Pt(acac)₂, Pt(PPh₃)₂Cl₂, PtCl₂, [Rh(cod)Cl]₂,Rh(acac)CO(PPh₃), Rh(acac)(CO)₂, Rh(cod)₂BF₄, RhCl(PPh₃)₃, RhCl₃×H₂O,Rh(acac)₃, [Os(CO)₃I₂]₂, [Os₃(CO)₁₂], OsH₄(PPH₃)₃, Cp₂Os, Cp*₂Os,H₂OsCl₆×6H₂O, OsCl₃×H₂O), and [(μ-Cl)Ir(η⁴-1,5-cod)]₂,[(μ-Cl)Ir(η²-coe)₂]₂, Ir(acac)₃, IrCl₃×n H₂O, (tht)₃IrCl₃,Ir(η³-allyl)₃, Ir(η³-methallyl)₃, in which cod is cyclooctadiene, coe iscyclooctene, acac is acetylacetonate and tht is tetrahydrothiophene. Themetal complexes can be prepared by processes known to those skilled inthe art or are commercially available.

In the case of preparation of iridium(III) complexes of the generalformula I (M in formula I is Ir), which are particularly preferredaccording to the present application, the aforementioned iridium(I) or(III) complexes can be used, especially [(μ-Cl)Ir(η⁴-1,5-cod)]₂,[(μ-Cl)Ir(η²-coe)₂]₂, Ir(acac)₃, IrCl₃×n H₂O, (tht)₃IrCl₃,Ir(η³-allyl)₃, Ir(η³-methallyl)₃, very particular preference being givento using [(β-Cl)Ir(η⁴-1,5-cod)]₂, in which cod is cyclooctadiene, coe iscyclooctene, acac is acetylacetonate and tht is tetrahydrothiophene.

Particular preference is given to effecting the inventive reaction ofthe carbene ligand precursor of the formula III with the suitable metalcomplex in the presence of a base and of an auxiliary reagent or of abasic auxiliary reagent, in which case the basic auxiliary reagent orthe auxiliary reagent comprises at least one metal selected from thegroup consisting of Ag, Hg, Sb, Mg, B and Al; preference is given toeffecting the inventive reaction in the presence of Ag₂O. A suitableprocess which can be employed correspondingly for the preparation of theinventive carbene complexes of the formula I is, for example, disclosedin WO 2007/088093.

In the case that Y is NR², the suitable ligand precursors of the formulaIII are prepared, for example, proceeding from ligand precursors of theformula IVa by alkylation, for example by methylation with MeI orMe₃OBF₄, or proceeding from ligand precursors of the formula IVb bycyclization, for example with CH(OEt)₃.

in which the symbols are each as defined above.

Other processes for preparing the ligand precursors of the formula IIIin which Y is NR² are also possible, as shown by way of examplehereinafter.

The compounds of the formulae IVa and IVb can be prepared by processesknown to those skilled in the art, suitable processes being mentioned inthe literature specified hereinafter.

Preparation processes for preparing very particularly preferredinventive carbene complexes of the formula I are illustrated by way ofexample hereinafter, the examples below comprising the preparation ofsuitable compounds of the formulae IVa and IVb and the preparation ofsuitable ligand precursors of the formula III proceeding fromcommercially available compounds or those preparable by processes knownto those skilled in the art. The compounds specified in the examplesbelow are illustrative and may be substituted according to thesubstitution pattern of the compounds of the formula I and/or haveheteroatoms in their ring systems according to the compounds of theformula I.

Synthesis of a triazolophenanthridine-based complex 2-alkyl from1,2,4-triazolo-[4,3-f]phenanthridine (A. G. Mikhailovskii, V. S.Shklyaev, Chem. Heterocycl. Comp. 1992, 445):

Synthesis of triazolophenanthridine-based complexes 2-aryl from6-chlorophenanthridine (A. G. Mikhailovskii, V. S. Shklyaev, Chem.Heterocycl. Comp. 1992, 445):

After the reaction, the inventive cyclometalated bridged carbene complexof the formula I is worked up and, if appropriate, purified by processesknown to those skilled in the art. Typically, the workup andpurification are effected by extraction, column chromatography and/orrecrystallization by processes known to those skilled in the art.

The inventive cyclometalated bridged carbene complexes of the formula Iare outstandingly suitable as phosphorescent emitter substances, sincethey have emission (electroluminescence) in the visible region of theelectromagnetic spectrum, preferably in the blue region of theelectromagnetic spectrum. With the aid of the inventive carbenecomplexes of the formula I as emitter substances, it is possible toprovide compounds which exhibit electroluminescence of good efficiency,the inventive carbene complexes being notable for good stability in thedevice. At the same time, the quantum yield is high.

In addition, the inventive carbene complexes of the formula I aresuitable as electron blockers, exciton blockers or hole blockers or holeconductors, electron conductors, hole injection layer or matrix materialin OLEDs, generally depending on the ligands used and the central metalused.

The present invention therefore further provides for the use of theinventive cyclometalated bridged carbene complexes of the formula I inorganic light-emitting diodes, preferably as emitter material, matrixmaterial, charge blocker material and/or charge transport material, morepreferably as emitter material, most preferably as a blue emitter.

Organic light-emitting diodes (OLEDs) are in principle formed fromseveral layers, for example:

1. Anode (1)

2. Hole-transporting layer (2)

3. Light-emitting layer (3)

4. Electron-transporting layer (4)

5. Cathode (5)

However, it is also possible that the OLED does not have all of thelayers mentioned; for example, an OLED with layers (1) (anode), (3)(light-emitting layer) and (5) (cathode) is likewise suitable, in whichcase the functions of layers (2) (hole-transporting layer) and (4)(electron-transporting layer) are assumed by the adjacent layers. OLEDswhich have layers (1), (2), (3) and (5) or layers (1), (3), (4) and (5)are likewise suitable.

The inventive cyclometalated bridged carbene complexes of the formula Ican be used in different layers of an OLED. A carbene complex of theformula I can be used in one layer of an OLED, but it is likewisepossible that two or more different carbene complexes of the formula Iare used in one or more layers of the OLED. For example, both theemitter material and the matrix material in the light-emitting layer ofthe OLED may comprise a carbene complex of the formula I, in which casethe carbene complex of the formula I used as the emitter material andthat used as the matrix material are generally different. It is likewisepossible that the emitter material and the hole conductor materialcomprise a carbene complex of the formula I, in which case the carbenecomplexes of the formula I are generally different. Further combinationsof different carbene complexes are possible and can be determined by theperson skilled in the art. The present invention therefore furtherprovides an OLED comprising at least one inventive cyclometalatedbridged carbene complex of the formula I. The inventive cyclometalatedbridged carbene complexes of the formula I are preferably used in thelight-emitting layer, for example as matrix molecules or emittermolecules, more preferably as emitter molecules. The present inventiontherefore further provides a light-emitting layer comprising at leastone inventive cyclometalated bridged carbene complex of the formula I,preferably as an emitter molecule. Preferred inventive cyclometalatedbridged carbene complexes of the formula I have been specified above.

The inventive cyclometalated bridged carbene complexes of the formula Imay be present in bulk—without further additives—in the light-emittinglayer or another layer of the OLED, preferably in the light-emittinglayer. However, it is likewise possible and preferred that, as well asthe inventive cyclometalated bridged carbene complexes of the formula I,further compounds are present in the layers comprising at least oneinventive cyclometalated bridged carbene complex of the formula I,preferably in the light-emitting layer. For example, a fluorescent dyemay be present in the light-emitting layer, in order to change theemission color of the inventive cyclometalated bridged carbene complexof the formula I used as an emitter molecule. In addition—in a preferredembodiment—a diluent material can be used.

This diluent material may be a polymer, for examplepoly(N-vinylcarbazole) or polysilane. However, the diluent material maylikewise be a small molecule, for example 4,4′-N,N′-dicarbazolebiphenyl(CDP=CBP) or tertiary aromatic amines. In addition, the carbene complexof the formula I in the light-emitting layer may be used together with amatrix material, suitable matrix materials being specified below. Theuse of the inventive carbene complexes of the formula I as a matrixmaterial (together with the use of the carbene complexes of the formulaI as an emitter material (in which case the carbene complexes used asthe matrix material and emitter material are generally different)) hasalready been mentioned above.

The individual layers of the OLED among those mentioned above may inturn be formed from 2 or more layers. For example, the hole-transportinglayer may be formed from a layer into which holes are injected from theelectrode and a layer which transports the holes away from the holeinjection layer into the light-emitting layer. The electron-transportinglayer may likewise consist of a plurality of layers, for example of alayer in which electrons are injected through the electrode, and a layerwhich receives electrons from the electron injection layer andtransports them into the light-emitting layer. The person skilled in theart is capable of selecting the structure of the OLEDs such that it isadjusted optimally to the inventive carbene complexes of the formula Iused in accordance with the invention, preferably as emitter substances.

In order to obtain particularly efficient OLEDs, the HOMO (highestoccupied molecular orbital) of the hole-transporting layer should bealigned to the work function of the anode, and the LUMO (lowestunoccupied molecular orbital) of the electron-transporting layer shouldbe aligned to the work function of the cathode.

The present application further provides an OLED comprising at least oneinventive light-emitting layer. The further layers in the OLED may beformed from any material which is typically used in such layers and isknown to those skilled in the art.

Suitable materials for the aforementioned layers (anode, cathode, holeand electron injection materials, hole and electron transport materials,and hole and electron blocker materials, matrix materials, fluorescenceand phosphorescence emitters) are known to those skilled in the art andare specified, for example, in H. Meng, N. Herron, Organic SmallMolecule Materials for Organic Light-Emitting Devices in OrganicLight-Emitting Materials and Devices, Ed.: Z. Li, H. Meng, Taylor &Francis, 2007, Chapter 3, pages 295 to 411.

The anode (1) is an electrode which provides positive charge carriers.It may be composed, for example, of materials which comprise a metal, amixture of different metals, a metal alloy, a metal oxide or a mixtureof different metal oxides. Alternatively, the anode may be a conductivepolymer. Suitable metals comprise the metals of groups 11, 4, 5 and 6 ofthe Periodic Table of the Elements, and also the transition metals ofgroups 8 to 10. When the anode is to be transparent, mixed metal oxidesof groups 12, 13 and 14 of the Periodic Table of the Elements aregenerally used, for example indium tin oxide (ITO). It is likewisepossible that the anode (1) comprises an organic material, for examplepolyaniline, as described, for example, in Nature, Vol. 357, pages 477to 479 (Jun. 11, 1992). At least either the anode or the cathode shouldbe at least partly transparent in order to be able to emit the lightformed.

Suitable hole transport materials for the layer (2) of the inventiveOLED are disclosed, for example, in Kirk-Othmer Encyclopedia of ChemicalTechnology, 4th Edition, Vol. 18, pages 837 to 860, 1996. Eitherhole-transporting molecules or polymers may be used as the holetransport material. Customarily used hole-transporting molecules areselected from the group consisting of4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 1,1-bis[(di-4-tolylamino)phenyl]-cyclohexane (TAPC),N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)-[1,1′-(3,3′-dimethyl)-biphenyl]-4,4′-diamine(ETPD), tetrakis(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA),α-phenyl-4-N,N-diphenylaminostyrene (TPS),p-(diethylamino)benzaldehydediphenylhydrazone (DEH), triphenylamine(TPA), bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane(MPMP),1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl]pyrazoline(PPR or DEASP), 1,2-trans-bis(9H-carbazol-9-yl)cyclobutane (DCZB),N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB),4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDTA), 4,4′,4″-tris(N-3-methyphenyl-N-phenylamino)triphenylamine (m-MTDATA),2,2,7,7-tetrakis(diphenylamino)-9,9-spirobifluorene (Spiro-TAD),4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA) and porphyrincompounds, and also phthalocyanines such as copper phthalocyanines.Customarily used hole-transporting polymers are selected from the groupconsisting of polyvinylcarbazoles, (phenylmethyl)polysilanes, PEDOT(poly(3,4-ethylenedioxythiophene)), preferably PEDOT doped with PSS(polystyrenesulfonate), and polyanilines. It is likewise possible toobtain hole-transporting polymers by doping hole-transporting moleculesinto polymers such as polystyrene and polycarbonate. Suitablehole-transporting molecules are the molecules already mentioned above.

Suitable electron transport materials for the layer (4) of the inventiveOLEDs comprise metals chelated with oxinoid compounds, such astris(8-hydroxyquinolato)aluminum (Alq₃) orbis(2-methyl-8-quinolato)-(p-phenylphenolato)aluminum (BALq) compoundsbased on phenanthroline such as2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA=BCP) or4,7-diphenyl-1,10-phenanthroline (BPhen) and azole compounds such as2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) and3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ),1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazoyl)phenylene (OXD7),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenylbenzimidazole) (TPBI). Thelayer (4) may serve both to ease the electron transport and as a bufferlayer or as a barrier layer in order to prevent quenching of the excitonat the interfaces of the layers of the OLED. The layer (4) preferablyimproves the mobility of the electrons and reduces quenching of theexciton.

Of the materials specified above as hole transport materials andelectron-transporting materials, some can fulfill a plurality offunctions. For example, some of the electron-conducting materials aresimultaneously hole-blocking materials when they have a low-lying HOMO.

The charge transport layers may also be electronically doped in order toimprove the transport properties of the materials used, in order firstlyto make the layer thicknesses more generous (avoidance of pinholes/shortcircuits) and secondly to minimize the operating voltage of the device.For example, the hole transport materials may be doped with electronacceptors; for example, phthalocyanines or arylamines such as TPD orTDTA may be doped with tetrafluorotetracyanoquinodimethane (F4-TCNQ).The electron transport materials may, for example, be doped with alkalimetals, for example Alg₃ with lithium. Electronic doping is known tothose skilled in the art and is disclosed, for example, in W. Gao, A.Kahn, J. Appl. Phys., Vol. 94, No. 1, Jul. 1, 2003 (p-doped organiclayers); A. G. Werner, F. Li, K. Harada, M. Pfeiffer, T. Fritz, K. Leo,Appl. Phys. Lett., Vol. 82, No. 25, Jun. 23, 2003 and Pfeiffer et al.,Organic Electronics 2003, 4, 89-103 and K. Walzer, B. Maennig, M.Pfeiffer, K. Leo, Chem. Soc. Rev. 2007, 107, 1233.

Suitable matrix materials are in principle the materials mentioned ashole and electron transport materials, and also carbene complexes, forexample the carbene complexes of the formula I or the carbene complexesmentioned in WO 2005/019373. Particularly suitable matrix materials arecarbazole derivatives, e.g.4,4′-bis(carbazol-9-yl)-2,2′-dimethylbiphenyl (CDBP),4,4′-bis(carbazol-9-yl)biphenyl (CBP), 1,3-bis(N-carbazolyl)benzene(mCP), and also the matrix materials mentioned in the applications whichwere yet to be published at the priority date of the present applicationand have the following reference numbers: PCT/EP2007/059648, EP 07 111824.4.

In the case that at least one emitter material is used in thelight-emitting layer of the inventive OLED together with at least onematrix material, the proportion of the at least one matrix material inthe light-emitting layer of the inventive OLED is generally from 10 to99% by weight, preferably from 50 to 99% by weight, more preferably from70 to 97% by weight. The proportion of the at least one emitter materialin the light-emitting layer is generally from 1 to 90% by weight,preferably from 1 to 50% by weight, more preferably from 3 to 30% byweight, where the proportions of the at least one matrix material andthe at least one emitter material add up to 100% by weight. However, itis also possible that the light-emitting layer, as well as the at leastone matrix material and the at least one emitter material, comprisesfurther substances, for example further diluent material, furtherdiluent material having been specified above.

The cathode (5) is an electrode which serves to introduce electrons ornegative charge carriers. The cathode may be any metal or nonmetal whichhas a lower work function than the anode. Suitable materials for thecathode are selected from the group consisting of alkali metals of group1, for example Li, Cs, alkaline earth metals of group 2, metals of group12 of the Periodic Table of the Elements, comprising the rare earthmetals and the lanthanides and actinides. In addition, metals such asaluminum, indium, calcium, barium, samarium and magnesium, andcombinations thereof, may be used. In addition, lithium-comprisingorganometallic compounds or LiF may be applied between the organic layerand the cathode in order to reduce the operating voltage.

The OLED of the present invention may additionally comprise furtherlayers which are known to those skilled in the art. For example, a layerwhich eases the transport of the positive charge and/or matches the bandgaps of the layers to one another may be applied between the layer (2)and the light-emitting layer (3). Alternatively, this further layer mayserve as a protective layer. In an analogous manner, additional layersmay be present between the light-emitting layer (3) and the layer (4) inorder to ease the transport of the negative charge and/or to match theband gaps between the layers to one another. Alternatively, this layermay serve as a protective layer.

In a preferred embodiment, the inventive OLED, in addition to the layers(1) to (5), comprises at least one of the further layers mentionedbelow:

-   -   a hole injection layer between the anode (1) and the        hole-transporting layer (2);    -   a blocking layer for electrons and/or excitons between the        hole-transporting layer (2) and the light-emitting layer (3);    -   a blocking layer for holes and/or excitons between the        light-emitting layer (3) and the electron-transporting layer        (4);    -   an electron injection layer between the electron-transporting        layer (4) and the cathode (5).

As already mentioned above, it is, however, also possible that the OLEDdoes not have all of the layers (1) to (5) mentioned; for example, anOLED having the layers (1) (anode), (3) (light-emitting layer) and (5)(cathode) is likewise suitable, in which case the functions of thelayers (2) (hole-transporting layer) and (4) (electron-transportinglayer) are assumed by the adjacent layers. OLEDs which have the layers(1), (2), (3) and (5) or the layers (1), (3), (4) and (5) are likewisesuitable.

Those skilled in the art know how suitable materials have to be selected(for example on the basis of electrochemical investigations). Suitablematerials for the individual layers and suitable OLED structures areknown to those skilled in the art and disclosed, for example, in WO2005/113704.

Furthermore, each of the specified layers of the inventive OLED may becomposed of two or more layers. In addition, it is possible that some orall of the layers (1), (2), (3), (4) and (5) have been surface-treatedin order to increase the efficiency of charge carrier transport. Theselection of the materials for each of the layers mentioned ispreferably determined by obtaining an OLED having a high efficiency.

The inventive OLED can be produced by methods known to those skilled inthe art. In general, the OLED is produced by successive vapor depositionof the individual layers onto a suitable substrate. Suitable substratesare, for example, glass or polymer films. For the vapor deposition,customary techniques may be used, such as thermal evaporation, chemicalvapor deposition and others. In an alternative process, the organiclayers may be coated from solutions or dispersions in suitable solvents,in which case coating techniques known to those skilled in the art areemployed. Compositions which, in addition to the at least one inventivecyclometalated bridged carbene complex of the formula I, have apolymeric material in one of the layers of the OLED, preferably in thelight-emitting layer, are generally applied as a layer by means ofsolution-processing processes.

In general, the different layers have the following thicknesses: anode(2) from 500 to 5000 Å, preferably from 1000 to 2000 Å;hole-transporting layer (3) from 50 to 1000 Å, preferably from 200 to800 Å; light-emitting layer (4) from 10 to 1000 Å, preferably from 100to 800 Å; electron-transporting layer (5) from 50 to 1000 Å, preferablyfrom 200 to 800 Å; cathode (7) from 200 to 10 000 Å, preferably from 300to 5000 Å. The position of the recombination zone of holes and electronsin the inventive OLED and thus the emission spectrum of the OLED may beinfluenced by the relative thickness of each layer. This means that thethickness of the electron transport layer should preferably be selectedsuch that the electron/hole recombination zone is within thelight-emitting layer. The ratio of the layer thicknesses of theindividual layers in the OLED is dependent upon the materials used. Thelayer thicknesses of any additional layers used are known to thoseskilled in the art.

Use of the inventive cyclometalated bridged carbene complexes of theformula I in at least one layer of the inventive OLED, preferably as anemitter molecule in the light-emitting layer of the inventive OLEDs,allows OLEDs with high efficiency and long lifetime to be obtained. Theefficiency of the inventive OLEDs may additionally be improved byoptimizing the other layers. For example, highly efficient cathodes suchas Ca, Ba or LiF may be used. Shaped substrates and novelhole-transporting materials which bring about a reduction in theoperating voltage or an increase in the external quantum efficiency arelikewise usable in the inventive OLEDs. Furthermore, additional layersmay be present in the OLEDs in order to adjust the energy level of thedifferent layers and to ease electroluminescence.

The inventive OLEDs may be used in all devices in whichelectroluminescence is useful. Suitable devices are preferably selectedfrom stationary and mobile visual display units, and also illuminatingmeans. Stationary visual display units are, for example, visual displayunits of computers, televisions, visual display units in printers,kitchen appliances and advertising panels, illuminations and informationpanels. Mobile visual display units are, for example, visual displayunits in cellphones, laptops, digital cameras, vehicles and destinationdisplays on buses and trains. Illuminating means are, for example,background lighting of LCDs, luminous surfaces, for example luminouswallpaper.

The inventive cyclometalated carbene complexes of the formula I,especially the preferred and particularly preferred embodiments of theinventive cyclometalated carbene complexes of the formula I specified inthe present application, may, in a preferred embodiment, be used in anOLED as described in application PCT/EP2008/058106, which was yet to bepublished at the priority date of the present application, in which casethe inventive cyclometalated carbene complex of the formula I preferablyreplaces the carbene complex of the general formula I present in thelight-emitting layer specified in PCT/EP2008/058106. The inventivecyclometalated carbene complexes can be used as phosphorescent emittersubstances in the OLED according to PCT/EP2008/058106. However, it isadditionally possible that the inventive cyclometalated carbenecomplexes of the formula I, depending on the central metal used and theligands used, and also on the further materials used in the OLEDs, areused as electron blockers, exciton blockers or hole blockers, or holeconductors, electron conductors, hole injection layers or matrixmaterial (especially as matrix material in the light-emitting layer).

In addition, the inventive cyclometalated bridged carbene complexes ofthe formula I may be used in OLEDs with inverse structure. The inventivecyclometalated bridged carbene complexes of the formula I are preferablyused in these inverse OLEDs again in the light-emitting layer. Thestructure of inverse OLEDs and the materials customarily used thereinare known to those skilled in the art.

The above-described inventive cyclometalated bridged carbene complexesof the formula I may, in addition to the use in OLEDs, be used ascolorants which emit in the visible region of the electromagneticspectrum on irradiation by light (photoluminescence).

The present application therefore further provides for the use of theabove-described inventive cyclometalated bridged carbene complexes ofthe formula I for the bulk coloration of polymeric materials.

Suitable polymeric materials are polyvinyl chloride, cellulose acetate,polycarbonates, polyamides, polyurethanes, polyimides,polybenzimidazoles, melamine resins, silicones, polyesters, polyethers,polystyrene, polymethyl methacrylate, polyethylene, polypropylene,polyvinyl acetate, polyacrylonitrile, polybutadiene,polychlorobutadiene, polyisoprene and the copolymers of the monomerslisted.

In addition, the above-described inventive cyclometalated bridgedcarbene complexes of the formula I may be used in the followingapplications:

-   -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as or in vat dye(s), for example for coloring        natural materials; examples are paper, wood, straw, leather,        pelts or natural fiber materials such as cotton, wool, silk,        jute, sisal, hemp, flax or animal hairs (for example horsehair)        and their conversion products, for example viscose fibers,        nitrate silk or copper rayon.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as colorants, for example for coloring paints,        varnishes and other surface coating compositions, paper inks,        printing inks, other inks and other colors for drawing and        writing purposes.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as pigmentary dyes, for example for coloring        paints, varnishes and other surface coating compositions, paper        inks, printing inks, other inks and other colors for drawing and        writing purposes.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as pigments in electrophotography: for example for        dry copying systems (Xerox process) and laser printers.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I for security marking purposes, for which high        chemical and photochemical stability and, if appropriate, also        the luminescence of the substances is of significance. This is        preferably for checks, check cards, banknotes, coupons,        documents, identification papers and the like, in which a        particular, unmistakable color impression is to be achieved.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as an additive to other colors in which a        particular shade is to be achieved; preference is given to        particularly brilliant colors.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I for marking articles for machine recognition of        these articles using the luminescence, preferably machine        recognition of articles for sorting, including, for example, for        the recycling of plastics.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as luminescent dyes for machine-readable markings;        preference is given to alphanumeric markings or barcodes.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I for adjusting the frequency of light, for example        to convert short-wavelength light into longer-wavelength,        visible light.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I in display elements for many kinds of display,        information and marking purposes, for example in passive display        elements, information signs and traffic signs, such as traffic        lights.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I in inkjet printers, preferably in homogeneous        solution as luminescent ink.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as a starting material for superconductive organic        materials.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I for solid-state luminescent markings.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I for decorative purposes.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I for tracer purposes, for example in biochemistry,        medicine, engineering and natural sciences. In this use, the        dyes can be bonded covalently to substrates or via secondary        valences such as hydrogen bonds or hydrophobic interactions        (adsorption).    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as luminescent dyes in high-sensitivity detection        methods (cf. C. Aubert, J. Fünfschilling, I. Zschocke-Gränacher        and H. Langhals, Z. Analyt. Chem. 320 (1985) 361).    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as luminescent dyes in scintillation devices.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in optical        light-collection systems.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in luminescent solar        collectors (cf. Langhals, Nachr. Chem. Tech. Lab. 28 (1980)        716).    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in        luminescence-activated displays (cf. W. Greubel and G. Baur,        Elektronik 26 (1977) 6).    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in cold light sources        for light-induced polymerization for the production of plastics.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes for materials testing,        for example in the production of semiconductor circuits.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes for the investigation        of microstructures of integrated semiconductor components.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in photoconductors.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in photographic        processes.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in display,        illumination or image conversion systems, in which excitation        occurs by means of electrons, ions or UV radiation, for example        in luminescent displays, Braun tubes or in fluorescent tubes.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes as part of an        integrated semiconductor circuit, the dyes being used as such or        in conjunction with other semiconductors, for example in the        form of epitaxy.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in chemiluminescent        systems, for example in chemiluminescent illumination rods, in        luminescent immunoassays or other luminescent detection methods.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes as signal colors,        preferably for the optical emphasis of inscriptions and drawings        or other graphical products, for individualizing signs and other        articles in which a particular optical color impression is to be        achieved.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes or luminescent dyes in dye lasers,        preferably as luminescent dyes for generating laser beams.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as active substances for nonlinear optics, for        example for frequency doubling and frequency tripling of laser        light.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as rheology improvers.    -   Use of the inventive cyclometalated bridged carbene complexes of        the formula I as dyes in photovoltaic arrays for the conversion        of electromagnetic radiation to electrical energy.

The examples which follow provide additional illustration of theinvention.

EXAMPLES I) Synthesis Methods Complexes with TriazolophenanthridineLigands Synthesis of 2-methyl

1-Methyl-1,2,4-triazolo[4,3-f]phenanthridinium tetrafluoroborate

A solution of 1,2,4-triazolo[4,3-f]phenanthridine (A. G. Mikhailovskii,V. S. Shklyaev, Chem. Heterocycl. Comp. 1992, 445) (5.9 g, 27 mmol) indichloromethane (200 ml) and methanol (20 ml) is admixed under argon at2° C. with trimethyloxonium tetrafluoroborate (4.3 g, 29 mmol) andstirred at 2° C. for 1 h and at room temperature for 16 h. The resultingprecipitate is filtered off and washed with dichloromethane, methanoland petroleum ether. Yield: 5.9 g (69%).

¹H NMR (d₆-DMSO, 400 MHz): δ=4.39 (s, 3H), 7.84-7.98 (m, 3H), 8.04 (td,1H), 8.41 (dd, 1H), 8.54 (dd, 1H), 8.83 (dd, 1H), 8.86 (dd, 1H), 11.47(s, 1H).

1-Methyl-1,2,4-triazolo[4,3-f]phenanthridinium iodide

A suspension of 1-methyl-1,2,4-triazolo[4,3-f]phenanthridiniumtetrafluoroborate (4.7 g, 5.9 mmol) in methanol (80 ml) is admixed underargon with tetrabutylammonium iodide (6.5 g, 17.6 mmol) and stirredunder reflux for 11 h. After cooling to room temperature, theprecipitate is filtered off and washed with methanol. Yield: 4.1 g of amixture of iodide and tetrafluoroborate salt (3:1, 83%).

Elemental analysis: calc. for C₁₄H₁₃IN₃/C₁₄H₁₃BF₄N₃ (3:1): C, 51.44; H,3.46; N, 12.00, 126.36. found: C, 51.4; H, 3.5; N, 12.0, 126.3.

mer-tris[1-Methyl-1,2,4-triazolo[4,3-f]phenanthridin-5-ylidene-C5,C6]iridium(III)

A suspension of 1-methyl-1,2,4-triazolo[4,3-f]phenanthridinium iodide(4.0 g, 11.0 mmol) and silver(I) oxide (1.3 g, 5.5 mmol) in methanol(200 ml) is stirred under argon at room temperature for 16 h. Themixture is diluted with methanol (70 ml) and stirred for a further 5 h.The precipitate is filtered off and washed with methanol and petroleumether. Yield: 4.9 g (94%). A mixture of the silver carbene (4.8 g, 5.1mmol) and of 1,5-cyclooctadieneiridium(I) chloride dimer (0.7 g, 1.1mmol) in mesitylene (200 ml) is stirred under reflux under argon for 20h. After cooling to room temperature, the precipitate is filtered offand washed with toluene. The combined filtrates are concentrated todryness and purified by column chromatography (alumina, 4:1dichloromethane/toluene). Yield: 1.4 g (75%).

¹H NMR (d₆-DMSO, 400 MHz): δ=3.47 (s, 3H), 3.60 (s, 3H), 3.68 (s, 3H),6.81 (d, 1H), 6.93 (d, 1H), 7.00-7.09 (m, 5H), 7.18 (d, 1H), 7.25 (d,1H), 7.68-7.76 (m, 3H), 7.81-7.96 (m, 6H), 8.30-8.38 (m, 3H), 8.56-8.64(m, 3H).

Synthesis of 2-o-tolyl

N-Phenanthridin-6-yl-N′-o-tolylhydrazine hydrochloride

A solution of o-tolylhydrazine hydrochloride (7.6 g, 47 mmol) indichloromethane (450 ml) is extracted by shaking three times each withsaturated aqueous sodium hydrogencarbonate solution (90 ml each time)and demineralized water. The organic phase is dried over sodium sulfate,filtered and concentrated to dryness. Yield: 4.9 g (86%). The hydrazine(4.8 g, 39 mmol) is dissolved in ethanol (100 ml) and admixed underargon with 6-chlorophenanthridine (A. G. Mikhailovskii, V. S. Shklyaev,Chem. Heterocycl. Comp. 1992, 445) (7.0 g, 33 mmol). The mixture isstirred under reflux for 16 h. After cooling to room temperature, theresulting precipitate is filtered off and washed with ethanol andpetroleum ether. Yield: 9.3 g (85%).

¹H NMR (d₆-DMSO, 400 MHz): δ=2.41 (s, 3H), 6.90 (t, 1H), 6.97 (d, 1H),7.11 (t, 1H), 7.20 (d, 1H), 7.60 (t, 1H), 7.74 (t, 1H), 7.92 (t, 1H),8.16 (t, 1H), 8.24 (d, 1H), 8.30 (br s, 1H), 8.71 (d, 1H), 8.88 (d, 1H),8.89 (d, 1H), 12.23 (br s, 1H), 13.02 (br s, 1H).

1-o-Tolyl-1,2,4-triazolo[4,3-f]phenanthridinium chloride

A suspension of N-phenanthridin-6-yl-N′-o-tolylhydrazine hydrochloride(9.0 g, 27 mmol) in triethyl orthoformate (360 ml) is stirred underreflux under argon for 17 h. After cooling to room temperature, theprecipitate is filtered off and washed with triethyl orthoformate andcold acetone. Yield: 8.2 g (88%).

¹H NMR (d₆-DMSO, 400 MHz): δ=2.47 (s, 3H), 7.56-7.73 (m, 3H), 7.81 (d,1H), 7.90-8.02 (m, 3H), 8.09 (t, 1H), 8.63 (d, 1H), 8.70 (d, 1H), 8.90(d, 1H), 8.93 (d, 1H), 12.22 (s, 1H).

mer-tris[1-o-Tolyl-1,2,4-triazolo[4,3-f]phenanthridin-5-ylidene-C5,C6]iridium(III)

A suspension of 1-o-tolyl-1,2,4-triazolo[4,3-f]phenanthridinium chloride(10.0 g, 28.8 mmol) and silver(I) oxide (3.3 g, 14.4 mmol) in methanol(1200 ml) is stirred under argon at room temperature for 44 h. Theprecipitate is filtered off and washed with methanol and petroleumether. Yield: 10.5 g (80%). A mixture of the silver carbene (10.5 g,11.6 mmol) and of 1,5-cyclooctadieneiridium(I) chloride dimer (1.6 g,2.3 mmol) in mesitylene (420 ml) is stirred under reflux under argon for16 h. After cooling to room temperature, the precipitate is filtered offand washed with dichloromethane. The combined filtrates are concentratedto dryness and the residue is purified by column chromatography(alumina, 1:1 dichloromethane/cyclohexane). Yield: 1.6 g (25%) offac-isomer and 1.5 g (25%) of mer-isomer.

fac-Isomer: ¹H NMR (CD₂Cl₂, 400 MHz): δ=1.51 (s, 9H), 6.47 (br s, 3H),6.65 (m_(c), 6H), 6.73 (d, 3H), 6.94 (dd, 3H), 7.01 (dd, 3H), 7.59 (dd,3H), 7.76 (d, 3H), 7.80 (dd, 3H), 8.23 (d, 3H), 8.45 (d, 3H).mer-Isomer: ¹H NMR (CD₂Cl₂, 400 MHz): δ=1.02 (s, 3H), 1.51 (s, 3H), 1.71(s, 3H), 5.85 (br s, 1H), 6.22 (br s, 1H), 6.29 (d, 1H), 6.44 (br s,1H), 6.52-6.74 (m, 7H), 6.80 (dd, 1H), 6.82 (dd, 1H), 7.00-7.14 (m, 3H),7.31 (br s, 1H), 7.40 (d, 1H), 7.49 (d, 1H), 7.56 (dd, 1H), 7.58 (dd,1H), 7.64 (dd, 1H), 7.69-7.84 (m, 5H), 8.28-8.43 (m, 6H).

Synthesis of 2-phenyl

N-Phenanthridin-6-yl-N′-phenylhydrazine hydrochloride

Phenylhydrazine (1.3 g, 12 mmol) is dissolved in ethanol (50 ml) andadmixed under argon with 6-chlorophenanthridine (A. G. Mikhailovskii, V.S. Shklyaev, Chem. Heterocycl. Comp. 1992, 445) (2.1 g, 10 mmol). Themixture is stirred under reflux for 16 h. After cooling to roomtemperature, the mixture is concentrated and the resulting precipitateis filtered off and washed with methyl tert-butyl ether. Yield: 2.6 g(82%).

¹H NMR (d₆-DMSO, 400 MHz): δ=6.95 (t, 1H), 7.10 (d, 2H), 7.29 (t, 2H),7.55 (br s, 1H), 7.69 (br t, 1H), 7.88 (br t, 1H), 8.11 (br s, 1H), 8.17(br s, 1H), 8.65 (br s, 1H), 8.84 (br s, 2H), 8.99 (br s, 1H), 12.30 (brs, 1H), 13.05 (br s, 1H).

1-Phenyl-1,2,4-triazolo[4,3-f]phenanthridinium chloride

A suspension of N-phenanthridin-6-yl-N′-phenylhydrazine hydrochloride(2.0 g, 6.2 mmol) in triethyl orthoformate (100 ml) is stirred underreflux under argon for 17 h. After cooling to room temperature, themixture is concentrated and the precipitate is filtered off and washedwith petroleum ether, methyl tert-butyl ether and acetone. Yield: 1.2 g(57%).

¹H NMR (d₆-DMSO, 400 MHz): δ=7.74 (t, 1H), 7.82 (t, 2H), 7.88-8.01 (m,3H), 8.08 (t, 1H), 8.31 (d, 2H), 8.68 (d, 1H), 8.80 (d, 1H), 8.86 (d,1H), 8.88 (d, 1H), 12.62 (s, 1H).

mer-tris[1-Phenyl-1,2,4-triazolo[4,3-f]phenanthridin-5-ylidene-C5,C6]iridium(III)

A suspension of 1-phenyl-1,2,4-triazolo[4,3-f]phenanthridinium chloride(1.18 g, 3.6 mmol) and silver(I) oxide (0.42 g, 1.8 mmol) in methanol(200 ml) is stirred under argon at room temperature for 32 h. Theprecipitate is filtered off and washed with methanol. Yield: 1.24 g(78%). A mixture of the silver carbene (1.24 g, 1.4 mmol) and of1,5-cyclooctadieneiridium(I) chloride dimer (0.19 g, 0.3 mmol) inmesitylene (100 ml) is stirred under reflux under argon for 16 h. Aftercooling to room temperature, the precipitate is filtered off and washedwith ethyl acetate. The combined filtrates are concentrated to drynessand the residue is purified by column chromatography (silica gel, 1:1ethyl acetate/cyclohexane). Yield: 0.03 g (5%) of fac-isomer, 0.01 g(2%) of mer-isomer and 0.34 g (57%) of isomer mixture.

fac-Isomer: ¹H NMR (CD₂Cl₂, 400 MHz): δ=6.16 (d, 6H), 6.88 (d, 3H), 6.93(dd, 6H), 7.11 (dd, 3H), 7.26 (dd, 3H), 7.63 (dd, 3H), 7.80 (dd, 3H),7.87 (d, 3H), 8.35 (d, 3H), 8.49 (d, 3H). ESI-MS: m/z=1074.2786 (calc.for M+H⁺: 1074.2778). mer-Isomer: ¹H NMR (CD₂Cl₂, 400 MHz): S=6.29-6.37(m, 2H), 6.44 (d, 1H), 6.47 (dd, 1H), 6.54 (dd, 2H), 6.66 (d, 1H), 6.78(dd, 1H), 6.95 (dd, 2H), 7.00-7.23 (m, 9H), 7.55-7.79 (m, 8H), 7.84 (d,1H), 8.15 (d, 1H), 8.29 (d, 1H), 8.34 (d, 1H), 8.39 (d, 1H), 8.43 (dd,2H), 8.55 (d, 1H), 8.98 (d, 1H).

Synthesis of 2-isopropyl

The complex 2-isopropyl is prepared analogously to the synthesis of2-methyl proceeding from 1,2,4-triazolo[4,3-f]phenanthridine (A. G.Mikhailovskii, V. S. Shklyaev, Chem. Heterocycl. Comp. 1992, 445).

ESI-MS: m/z=973 (calc. for M+H⁺: 973).

Synthesis of 2-p-pyridyl

The complex 2-p-pyridyl is prepared analogously to the synthesis of2-phenyl proceeding from chlorophenanthridine (A. G. Mikhailovskii, V.S. Shklyaev, Chem. Heterocycl. Comp. 1992, 445) and 4-hydrazinopyridine(E. M. Isin, M. Jonge, N. Castagnoli, J. Org. Chem. 2001, 66, 4220).

2-p-Pyridyl: ESI-MS: m/z=1078 (calc. for M+H⁺: 1078).

II) Photophysical Characterization

The photoluminescence of the emitting complexes was carried out in thinPMMA films (polymethyl methacrylate) with an emitter doping of 2%. Thefilms were produced as follows: 2 mg/l of emitter were dissolved in a10% PMMA solution in DCM (Mw 120 kD) and applied to a microscope slidewith a 60 μm doctor blade. The excitation was effected at a wavelengthof 325 nm (HeCd laser) at right angles to the microscope slide, and theemission was detected at an angle of 45° by means of fiber optics in adiode array spectrometer.

Complex λ_(max) [nm] QA [%] CIE x CIE y 2-Methyl (mer-isomer) 448, 48145 0.15 0.18 2-Phenyl (fac-isomer) 448, 475 45 0.15 0.17 2-Phenyl(mer-isomer) 452, 478 65 0.15 0.18 2-o-Tolyl (fac-isomer) 445, 473 710.15 0.15 2-o-Tolyl (mer-isomer) 449, 475 49 0.15 0.18

III) OLED Device Tests

III.1) Light-Emitting Layer: Compound of the Formula I+Silylcarbazole

The ITO substrate used as the anode is first cleaned with commercialdetergents for LCD production (Deconex® 20NS and 250RGAN-ACID®neutralizing agent) and then in an acetone/isopropanol mixture in anultrasound bath. To eliminate possible organic residues, the substrateis exposed to a continuous ozone flow in an ozone oven for a further 25minutes. This treatment also improves the hole injection of the ITO.

Thereafter, the organic materials mentioned below are applied by vapordeposition to the cleaned substrate at a rate of 0.5-5.0 nm/min at about10⁻⁸ mbar. As a hole conductor and exciton blocker, the compound V1 isfirst applied to the substrate in a layer thickness of 45 nm.

(for the preparation of compound V1, see Ir complex (7) in WO2005/019373.)

Subsequently, a mixture of 6.5% by weight of the compound 2-methyl

and 93.5% by weight of the compound V2

(for the preparation of compound V2, see example (4b) in the applicationEP 07 111 824.4, which was yet to be published at the priority date ofthe present application (title: “Organic light-emitting diodescomprising at least one disilyl compound selected fromdisilylcarbazoles, disilyldibenzofurans, disilyldibenzothiophenes,disilyldibenzophospholes, disilyldibenzo-thiophene S-oxides anddisilyldibenzothiophene S,S-dioxides”).

is applied by vapor deposition in a thickness of 40 nm, 2-methylfunctioning as an emitter and V2 as a matrix material. Thereafter, anexciton blocker layer composed of V2 is applied by vapor deposition in athickness of 10 nm.

Thereafter, an electron conductor layer composed of BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) is applied by vapordeposition in a thickness of 45 nm, as are a 0.7 nm-thick lithiumfluoride layer and finally a 100 nm-thick Al electrode.

To characterize the OLEDs, electroluminescence spectra are recorded atvarious currents and voltages. In addition, the current-voltagecharacteristic is measured in combination with the emitted light output.The light output can be converted to photometric parameters bycalibration with a photometer. To determine the lifetime, the OLED isoperated at a constant current density and the decrease in the lightoutput is recorded. The lifetime is defined as that time which elapsesuntil the luminance has decreased to half of the initial luminance.

For the OLED described, the following electrooptical data are obtained:

Emission maximum 452, 479 nm CIE(x, y) 0.15; 0.18 Photometric efficiency13.4 cd/A (max.) External quantum yield 7.2% (max.) Maximum luminance1300 cd/m² (max.)III.2) Light-Emitting Layer: Compound of the Formula I+Ir(dpbic)₃

The ITO substrate used as the anode is first cleaned with commercialdetergents for LCD production (Deconex® 20NS and 250RGAN-ACID®neutralizing agent) and then in an acetone/isopropanol mixture in anultrasound bath. To eliminate possible organic residues, the substrateis exposed to a continuous ozone flow in an ozone oven for a further 25minutes. This treatment also improves the hole injection properties ofthe ITO.

Thereafter, the organic materials specified below are applied by vapordeposition to the cleaned substrate at a rate of approx. 0.5-5 nm/min atabout 10⁻⁸ mbar. The hole conductor and exciton blocker applied to thesubstrate is Ir(dpbic)₃ with a thickness of 45 nm.

(for preparation see Ir complex (7) in application WO 2005/019373).

Subsequently, a mixture of 7% by weight of the compound 2-R

and 93% by weight of the compound Ir(dpbic)₃ is applied by vapordeposition in a thickness of 40 nm, the former compound functioning asthe emitter, the latter as the matrix material.

Subsequently, the material9-(4-phenyl)-3,6-bis(triphenylsilyl)-9H-carbazole is applied by vapordeposition with a thickness of 10 nm as an exciton and hole blocker.

Next, an electron transporter BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) is applied by vapordeposition in a thickness of 45 nm, as are a 0.75 nm-thick lithiumfluoride layer and finally a 110 nm-thick Al electrode.

To characterize the OLEDs, electroluminescence spectra are recorded atdifferent currents and voltages. In addition, the current-voltagecharacteristic is measured in combination with the light output emitted.The light output can be converted to photometric parameters bycalibration with a photometer.

For the OLEDs described, the following electrooptical data are obtained:

Emission Photometric Power External Luminance maximum efficiency atefficiency at quantum yield at 10 V R = Material (nm) CIE (x, y) 4 V(cd/A) 4 V (lm/W) at 4 V (%) (cd/m²) methyl

451/478 0.16; 0.21 13.2 10.4 7.1 490 o-tolyl

455/478 0.17; 0.2 7.7 6.0 5.1 810 o-tolyl

448/476 0.16; 0.16 9.1 7.2 6.7 740 i-propyl

449/476 0.16; 0.19 14.6 11.4 9.9 575 phenyl

449/476 nm 0.16; 0.17 15 11.8 11.2 890

1. A cyclometalated carbene complex of the general formula (I)

in which the symbols are each defined as follows: M is a metal atomselected from the group consisting of metals of group IB, IIB, IIIB,IVB, VB, VIIB, VIIB, VIIIB, the lanthanides and IIIA of the PeriodicTable of the Elements (CAS version) in any oxidation state possible forthe appropriate metal atom; K is an uncharged mono- or bidentate ligand;L is a mono- or dianionic ligand; X is CR¹ or N; Y is NR² or CR² ₂; A,D, G, E, A′, D′, G′ and E′ are each independently CH, CR³ or N; R¹ is F,CN, C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio,substituted or unsubstituted C₆-C₃₀-aryl or substituted or unsubstitutedheteroaryl having from 5 to 30 ring atoms; R², R³ are each independentlysubstituted or unsubstituted C₁-C₂₀-alkyl, substituted or unsubstitutedC₅-C₂₀-cycloalkyl, substituted or unsubstituted C₅-C₂₀-cycloalkenyl,substituted or unsubstituted heterocycloalkyl having from 5 to 30 ringatoms, substituted or unsubstituted heterocycloalkenyl having from 5 to30 ring atoms, substituted or unsubstituted C₂-C₂₀-alkenyl, substitutedor unsubstituted C₂-C₂₀-alkynyl, substituted or unsubstitutedC₆-C₃₀-aryl, substituted or unsubstituted heteroaryl having from 5 to 30ring atoms or a substituent with donor or acceptor action selected fromthe group consisting of: C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy,C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals,halogenated C₁-C₂₀-alkyl radicals, carbonyl (—CO(R⁴)), carbonylthio(—C═O(SR⁴)), carbonyloxy (—C═O(OR⁴)), oxycarbonyl (—OC═O(R⁴)),thiocarbonyl (—SC═O(R⁴)), amino (—NR⁴R⁵), OH, pseudohalogen radicals,amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵), phosphonate (—P(O)(OR⁴)₂), phosphate(—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵), phosphine oxide (—P(O)R⁴ ₂), sulfate(—OS(O)₂OR⁴), sulfoxide (—S(O)R⁴), sulfonate (—S(O)₂OR⁴), sulfonyl(—S(O)₂R⁴), sulfonamide (—S(O)₂NR⁴R⁵), NO₂, boronic esters (—B(OR⁴)₂),imino (—C═NR⁴R⁵), borane radicals, stannate radicals, hydrazineradicals, hydrazone radicals, oxime radicals, nitroso groups, diazogroups, vinyl groups, sulfoximines, alanes, germanes, boroxines andborazines; or two adjacent R³ radicals together form a saturated orunsaturated, substituted or unsubstituted bridge comprising from 3 to 6atoms, wherein the R³ radicals together with one of the elements A=D,D-E, D′-E′, E′=G′ form a 5- to 8-membered ring; or the R³ radicals atthe G′ and A positions together form a saturated or unsaturated,substituted or unsubstituted bridge comprising from 1 to 4 atoms,wherein the R³ radicals together with the element -G′-C—C-A- form a 5-to 8-membered ring; R⁴, R⁵, R⁶ are each independently H, substituted orunsubstituted C₁-C₂₀-alkyl or substituted or unsubstituted C₆-C₃₀-arylor substituted or unsubstituted heteroaryl having from 5 to 30 ringatoms; n is a number of carbene ligands, where n is at least 1 and thecarbene ligands in the complex of the formula I, when n>1, are the sameor different; m is a number of ligands K, where m is 0 or ≧1, and theligands K, when m>1, are the same or different; o is a number of ligandsL, where o is 0 or ≧1, and the ligands L, when o>1, are the same ordifferent; where the sum of n+m+o depends on the oxidation state andcoordination number of the metal atom used and on the denticity of theligands L and K, and also on the charge of the ligand L, with thecondition that n is at least
 1. 2. The carbene complex according toclaim 1, wherein M is Ir(III), n is 3, and m, o are each
 0. 3. Thecarbene complex according to claim 1, wherein R², R³ are eachindependently selected from the group consisting of substituted orunsubstituted C₁-C₂₀-alkyl, substituted or unsubstituted C₂-C₂₀-alkenyl,substituted or unsubstituted C₂-C₂₀-alkynyl, substituted orunsubstituted C₆-C₃₀-aryl, substituted or unsubstituted heteroarylhaving from 5 to 30 ring atoms, C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy,C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals,halogenated C₁-C₂₀-alkyl radicals and pseudohalogen radicals; or twoadjacent R³ radicals together form a saturated or unsaturated, methyl-,methoxy-, phenyl-, SiMe₃-, SiPh₃-, F-, CF₃- or CN-substituted orunsubstituted bridge comprising 3 or 4 carbon atoms, wherein the R³radicals together with one of the elements A=D, D-E, A′=D′, D′-E′, E′=G′form a 5- or 6-membered ring; or the R³ radicals at the G′ and Apositions together form a saturated or unsaturated, methyl-, methoxy-,phenyl-, SiMe₃-, SiPh₃-, F—, CF₃— or CN-substituted or unsubstitutedbridge comprising 1 or 2 carbon atoms, wherein the R³ radicals togetherwith the element -G′-C—C-A- form a 5- or 6-membered ring.
 4. The carbenecomplex according to claim 1, wherein R² is selected from the groupconsisting of substituted or unsubstituted C₁-C₂₀-alkyl which isbranched in the 1-position, substituted or unsubstituted C₆-aryl, andsubstituted or unsubstituted heteroaryl having from 5 to 13 ring atoms.5. The carbene complex according to claim 1, wherein X is N, and is NR².6. The carbene complex according to claim 1, wherein A, D, G, E, A′, D′,G′ and E′ are each CH or CR³.
 7. The carbene complex according to claim1, wherein the carbene complex is selected from the group consisting of

in which: A, D, G, E, A′, D′, G′ and E′ are each independently CH, CR³or N, preferably CH or CR³; R², R³ are each independently substituted orunsubstituted C₁-C₂₀-alkyl, substituted or unsubstitutedC₅-C₂₀-cycloalkyl, substituted or unsubstituted C₅-C₂₀-cycloalkenyl,substituted or unsubstituted heterocycloalkyl having from 5 to 30 ringatoms, substituted or unsubstituted heterocycloalkenyl having from 5 to30 ring atoms, substituted or unsubstituted C₂-C₂₀-alkenyl, substitutedor unsubstituted C₂-C₂₀-alkynyl, substituted or unsubstitutedC₆-C₃₀-aryl, substituted or unsubstituted heteroaryl having from 5 to 30ring atoms or a substituent with donor or acceptor action selected fromthe group consisting of: C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy,C₁-C₂₀-alkylthio, C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals,halogenated C₁-C₂₀-alkyl radicals, carbonyl (—CO(R⁴)), carbonylthio(—C═O(SR⁴)), carbonyloxy (—C═O(OR⁴)), oxycarbonyl (—OC═O(R⁴)),thiocarbonyl (—SC═O(R⁴)), amino (—NR⁴R⁵), OH, pseudohalogen radicals,amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵), phosphonate (—P(O)(OR⁴)₂), phosphate(—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵), phosphine oxide (—P(O)R⁴ ₂), sulfate(—OS(O)₂OR⁴), sulfoxide (—S(O)R⁴), sulfonate (—S(O)₂OR⁴), sulfonyl(—S(O)₂R⁴), sulfonamide (—S(O)₂NR⁴R⁵), NO₂, boronic esters (—B(OR⁴)₂),imino (—C═NR⁴R⁵), borane radicals, stannate radicals, hydrazineradicals, hydrazone radicals, oxime radicals, nitroso groups, diazogroups, vinyl groups, sulfoximines, alanes, germanes, boroxines andborazines; or two adjacent R³ radicals together form a saturated orunsaturated, substituted or unsubstituted bridge composed of from 3 to 6atoms, wherein the R³ radicals together with one of the elements A=D,D-E, A′=D′, D′-E′, E′=G′ form a 5- to 8-membered ring; or the R³radicals at the G′ and A positions together form a saturated orunsaturated, substituted or unsubstituted bridge composed of from 1 to 4atoms, wherein the R³ radicals together with the element -G′-C—C-A- forma 5- to 8-membered ring; R⁴, R⁵, R⁶ are each independently H,substituted or unsubstituted C₁-C₂₀-alkyl or substituted orunsubstituted C₆-C₃₀-aryl, or substituted or unsubstituted heteroarylhaving from 5 to 30 ring atoms; Y is CR² ₂; M is Ir, Os or Pt; K is anuncharged bidentate ligand; L is a monoanionic bidentate ligand; n isthe number of carbene ligands, where n is 3 in the case of Ir, is 2 inthe case of Os and is 1 or 2 in the case of Pt, and the carbene ligandsin the complexes of the formulae Ia, Ib, Ic and Id are the same ordifferent; m is 0 in the case that M=Ir or Pt and is 1 in the case ofOs; o is 0 in the case that M=Ir or Os and Pt and in the case that n=2,and is 1 in the case of Pt and in the case that n=1.
 8. A process forpreparing a carbene complex according to claim 1, comprising a reactionof at least one ligand precursor of the formula (III)

in which Q is a monoanionic counterion; X is CR¹ or N; Y is NR² or CR²₂; A, D, G, E, A′, D′, G′ or E′ are each independently CH, CR³ or N; R¹is F, CN, C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,C₆-C₃₀-arylthio, substituted or unsubstituted C₆-C₃₀-aryl or substitutedor unsubstituted heteroaryl having from 5 to 30 ring atoms; R², R³ areeach independently substituted or unsubstituted C₁-C₂₀-alkyl,substituted or unsubstituted C₅-C₂₀-cycloalkyl, substituted orunsubstituted C₅-C₂₀-cycloalkenyl, substituted or unsubstitutedheterocycloalkyl having from 5 to 30 ring atoms, substituted orunsubstituted heterocycloalkenyl having from 5 to 30 ring atoms,substituted or unsubstituted C₂-C₂₀-alkenyl, substituted orunsubstituted C₂-C₂₀-alkynyl, substituted or unsubstituted C₆-C₃₀-aryl,substituted or unsubstituted heteroaryl having from 5 to 30 ring atomsor a substituent with donor or acceptor action selected from the groupconsisting of: C₁-C₂₀-alkoxy, C₆-C₃₀-aryloxy, C₁-C₂₀-alkylthio,C₆-C₃₀-arylthio, SiR⁴R⁵R⁶, halogen radicals, halogenated C₁-C₂₀-alkylradicals, carbonyl (—CO(R⁴)), carbonylthio (—C═O(SR⁴)), carbonyloxy(—C═O(OR⁴)), oxycarbonyl (—OC═O(R⁴)), thiocarbonyl (—SC═O(R⁴)), amino(—NR⁴R⁵), OH, pseudohalogen radicals, amido (—C═O(NR⁴R⁵)), —NR⁴C═O(R⁵),phosphonate (—P(O)(OR⁴)₂), phosphate (—OP(O)(OR⁴)₂), phosphine (—PR⁴R⁵),phosphine oxide (—P(O)R⁴ ₂), sulfate (—OS(O)₂OR⁴), sulfoxide (—S(O)R⁴),sulfonate (—S(O)₂OR⁴), sulfonyl (—S(O)₂R⁴), sulfonamide (—S(O)₂NR⁴R⁵),NO₂, boronic esters (—B(OR⁴)₂), imino (—C═NR⁴R⁵), borane radicals,stannate radicals, hydrazine radicals, hydrazone radicals, oximeradicals, nitroso groups, diazo groups, vinyl groups, sulfoximines,alanes, germanes, boroxines and borazines; or two adjacent R³ radicalstogether form a saturated or unsaturated, substituted or unsubstitutedbridge composed of from 3 to 6 atoms, wherein the R³ radicals togetherwith one of the elements A=D, D-E, A′=D′, D′-E′, E′=G′ form a 5- to8-membered ring; or the R³ radicals at the G′ and A positions togetherform a saturated or unsaturated, substituted or unsubstituted bridgecomposed of from 1 to 4 atoms, wherein the R³ radicals together with theelement -G′-C—C-A- form a 5- to 8-membered ring; and R⁴, R⁵, R⁶ are eachindependently H, substituted or unsubstituted C₁-C₂₀-alkyl orsubstituted or unsubstituted C₆-C₃₀-aryl or substituted or unsubstitutedheteroaryl having from 5 to 30 ring atoms; with a metal complexcomprising at least one metal M where M is a metal atom selected fromthe group consisting of metals of group IB, IIB, IIIB, IVB, VB, VIIB,VIIB, VIIIB, the lanthanides and IIIA of the Periodic Table of theElements (CAS version) in any oxidation state possible for theappropriate metal atom.
 9. The process according to claim 8, wherein themetal M used is Ir, Os or Pt.
 10. An organic light-emitting diodecomprising at least one carbene complex according to claim
 1. 11. Alight-emitting layer comprising at least one carbene complex accordingto claim
 1. 12. An organic light-emitting diode comprising at least onelight-emitting layer according to claim
 11. 13. A device selected fromthe group consisting of stationary visual display units, mobile visualdisplay units, and illuminating means, comprising at least one organiclight-emitting diode according to claim
 12. 14. A device selected fromthe group consisting of stationary visual display units, mobile visualdisplay units and illuminating means, comprising at least one organiclight-emitting diode according to claim
 10. 15. The carbene complexaccording to claim 1, wherein M is Fe, Os, Co, Rh, Ir, Ni, Ru, Pd, Pt,Cu, Au, Ce, Tb, or Eu.
 16. The carbene complex according to claim 3,wherein R³ is selected from the group consisting of methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tolyl,dimethylphenyl, trimethylphenyl, pyridyl, thienyl, pyrrolyl, furyl,thiazolyl, oxazolyl, pyrazolyl, imidazolyl, methoxy, phenoxy, SCH₃, SPh,SiR⁴R⁵R⁶, F, Cl, Br, CF₃, and CN.
 17. The carbene complex according toclaim 1, wherein L is a monoanionic ligand.
 18. The carbene complexaccording to claim 1, wherein X is N.
 19. The carbene complex accordingto claim 4, wherein R² is selected from the group consisting ofisopropyl, isobutyl, isopentyl, sec-butyl, tert-butyl, 2-tolyl,2-methoxyphenyl, 2-cyanophenyl, 2-trifluoromethylphenyl,2,6-difluorophenyl, 2,3-, 2,4-, 2,5- and 2,6-dimethylphenyl or 2,4,6-,2,3,4- and 2,3,5-trimethylphenyl; pyridin-2-yl, pyridin-3-yl,pyridin-4-yl, thiophen-2-yl, thiophen-3-yl, pyrrol-2-yl, pyrrol-3-yl,furan-2-yl, furan-3-yl, thiazol-2-yl, oxazol-2-yl, pyrazol-3-yl andimidazol-2-yl.